XML 1143 R90.htm IDEA: XBRL DOCUMENT
v2.4.0.8

Contingencies and Commitments - Additional Information (Detail) In Millions, unless otherwise specified | 1 Months Ended | 3 Months Ended | 12 Months Ended |  |  | 1 Months Ended | 12 Months Ended |  | 12 Months Ended | 3 Months Ended | 0 Months Ended | 1 Months Ended | 3 Months Ended | 12 Months Ended |  | 12 Months Ended |  | 0 Months Ended | 12 Months Ended | 3 Months Ended | 6 Months Ended | 12 Months Ended | 0 Months Ended |
--- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | --- | ---
Jul. 31, 2012 Plant | Jun. 12, 2012 USD ($) Installment | Jun. 12, 2012 EUR (€) | Dec. 31, 2013 USD ($) | Jun. 30, 2013 USD ($) | Dec. 31, 2013 USD ($) | Dec. 31, 2012 USD ($) | Dec. 31, 2011 USD ($) | Mar. 26, 2012 USD ($) | Mar. 26, 2012 EUR (€) | Jun. 30, 2010 t | Nov. 30, 2006 Curtis v. Alcoa Inc. [Member] Person | Dec. 31, 2011 Scrg Brownfield Recovery Corp Energy Answers Corporation of Puerto Rico [Member] USD ($) | Feb. 21, 2013 Minimum [Member] USD ($) | Feb. 21, 2013 Maximum [Member] USD ($) | Feb. 21, 2013 Maximum [Member] EUR (€) | Feb. 21, 2013 Alcoa Trasformazioni [Member] USD ($) | Feb. 21, 2013 Alcoa Trasformazioni [Member] EUR (€) | Dec. 31, 2013 Alcoa [Member] USD ($) | Dec. 31, 2013 Alcoa [Member] EUR (€) | Dec. 31, 2013 Alumina [Member] | Jun. 30, 2013 Aluminium Bahrain [Member] USD ($) | Oct. 09, 2012 Alba [Member] USD ($) Installment | Feb. 27, 2008 Alba [Member] USD ($) | Feb. 27, 2008 Alba [Member] | Sep. 30, 2012 Alba [Member] USD ($) | Jun. 30, 2012 Alba [Member] USD ($) | Dec. 31, 2013 Alba [Member] | Oct. 09, 2013 Alba [Member] USD ($) | Dec. 31, 2013 Department of Justice [Member] USD ($) Installment | May 31, 2011 Breaches of Warranty [Member] USD ($) | Jan. 20, 2011 Breaches of Warranty [Member] Scrg Brownfield Recovery Corp Energy Answers Corporation of Puerto Rico [Member] USD ($) | Jan. 20, 2011 Punitive Damages [Member] Scrg Brownfield Recovery Corp Energy Answers Corporation of Puerto Rico [Member] USD ($) | Jan. 20, 2011 Property Damages [Member] Scrg Brownfield Recovery Corp Energy Answers Corporation of Puerto Rico [Member] USD ($) | May 31, 2011 Negligence Award [Member] USD ($) | Dec. 31, 2013 Securities and Exchange Commission [Member] USD ($) Installment | Dec. 31, 2013 Department of Justice and Securities Exchange Commission [Member] USD ($) | Dec. 31, 2013 Department of Justice and Securities Exchange Commission [Member] USD ($) | Dec. 31, 2013 Alcoa World Alumina and Chemicals [Member] Country | Dec. 31, 2013 Alcoa World Alumina and Chemicals [Member] Alcoa [Member] | Dec. 31, 2013 Alcoa World Alumina and Chemicals [Member] Alumina [Member] | Nov. 19, 2009 Italian Government [Member] USD ($) Plant | Nov. 19, 2009 Italian Government [Member] EUR (€) Plant | Jul. 31, 2006 Italian Government [Member] | Dec. 31, 2012 Portovesme [Member] Ton
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Period of alleged conspiracy, years |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 15 years |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Damages claimed, value |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 1,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Agreed amount payable on settlement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 85 |  |  |  |  |  |  | 223 |  |  |  |  |  | 175 |  |  |  |  |  |  |  |  |
Litigation settlement number of installments |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 2 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Contingency settlement agreement amount paid |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 42.5 |  |  |  |  |  | 42.5 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Contingency settlement agreement future payable date |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | October 9, 2013 |  | AWA agreed to pay a total of $223, including a fine of $209 payable in five equal installments over four years. The first installment of $41.8, plus a one-time administrative forfeiture of $14, will be paid in the first quarter of 2014 (paid on January 22,2014), and the remaining installments of $41.8 each will be paid in the first quarters of 2015-2018. |  |  |  |  |  | The Company agreed to a settlement amount of $175, but will be given credit for the $14 one-time forfeiture payment, which is part of the DOJ resolution, resulting in a total cash payment to the SEC of $161 payable in five equal installments over four years. The first installment of $32.2 will be paid to the SEC in the first quarter of 2014 (paid on January 22, 2014), and the remaining installments of $32.2 each will be paid in the first quarters of 2015-2018. |  |  |  |  |  |  |  |  |
Cash payment for suit settlement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 103 |  |  |  | 40 |  |  |  |  |  |  |  |  |  | 161 |  |  |  |  |  |  |  |  |
Restructuring and other charges |  |  |  |  |  | 782 | 172 | 281 |  |  |  |  |  |  |  |  |  |  |  |  |  | 103 |  |  |  |  | 45 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Amount of settlement offer rejected |  |  |  |  | 60 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Charges recorded of settlement amount |  |  |  | 288 | 0 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 288 |  |  |  |  |  |  |  |
Agreement settlement effective date |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | Jan. 09, 2014 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of installments |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 5 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of years in which installments is payable |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 4 years |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Fine payable over four years period |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 209 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
First installment payable on settlement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 41.8 |  |  |  |  |  | 32.2 |  |  |  |  |  |  |  |  |
One-time administrative forfeiture amount |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 14 |  |  |  |  |  | 14 |  |  |  |  |  |  |  |  |
Installments payable in first quarters of 2015 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 41.8 |  |  |  |  |  | 32.2 |  |  |  |  |  |  |  |  |
Installments payable in first quarters of 2016 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 41.8 |  |  |  |  |  | 32.2 |  |  |  |  |  |  |  |  |
Installments payable in first quarters of 2017 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 41.8 |  |  |  |  |  | 32.2 |  |  |  |  |  |  |  |  |
Installments payable in first quarters of 2018 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 41.8 |  |  |  |  |  | 32.2 |  |  |  |  |  |  |  |  |
Number of installments |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 5 |  |  |  |  |  |  |  |  |
Number of years in which installments is payable |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 4 years |  |  |  |  |  |  |  |  |
Legal costs |  |  |  |  |  | 391 | 85 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 7 |  |  |  |  |  |  |  |
Charges in respect of the investigations |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 103 |  |  |  |  |  |  |
Number of countries |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 7 |  |  |  |  |  |
Percentage owns on settlement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 60.00% | 40.00% |  |  |  |
Civil settlement |  |  |  |  |  | 85 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Government investigations and legal charges |  |  |  |  |  | 384 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Percentage to allocate cost of Alba civil settlement and all legal fees |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 85.00% | 85.00% | 15.00% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Percentage of civil settlement and all legal costs associated with civil suit and government investigations |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 60.00% | 60.00% | 40.00% |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Retired former employees involved in class action |  |  |  |  |  |  |  |  |  |  |  | 13,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Trial length, number of days |  |  |  |  |  | 8 days |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Court granted motion for judgment regarding Plaintiffs |  |  |  |  |  |  |  |  |  |  |  |  | 20 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 13 | 6 | 10 | 10 |  |  |  |  |  |  |  |  |  |
Damages awarded to plaintiff, pre-judgment interest |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 2 |  |  |  |  |  |  |  |  |  |  |  |  |  |
Management estimate for maximum exposure from class action |  |  |  |  |  |  |  |  | 110 | 85 |  |  |  |  |  |  | 97 | 76 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Provision for contract losses |  |  |  |  |  |  |  |  |  |  |  |  |  | 0 | 97 | 76 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of years operating under a power supply structure |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 10 years |
Charge related to European Commission announcement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 250 | 173 |  |
Number of smelters | 2 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 2 | 2 |  |
Write-off of receivable |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 20 | 14 |  |
Establishment reserve |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 230 | 159 |  |
Recovery amount |  | 375 | 303 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Reduction in recovery amount |  | 65 | 53 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Payments to Italian Government |  | 310 | 250 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Payments to Italian Government, installments amount |  | 69 | 50 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of installments, litigation payment |  | 5 | 5 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Litigation reserve |  | 219 | 159 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 0 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Range of reasonable possible loss, minimum |  | 219 | 159 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Range of reasonable possible loss, maximum |  | 418 | 303 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Noncurrent asset |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 126 | € 91 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Amount of curtailment, metric-tons-per-year |  |  |  |  |  |  |  |  |  |  | 44,000 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 150,000

X
- Definition Amount of curtailment. + References No definition available. + Details
Name: | aa_AmountOfCurtailment
Namespace Prefix: | aa_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition Charge related to European commission announcement. + References No definition available. + Details
Name: | aa_ChargeRelatedToEuropeanCommissionAnnouncement
Namespace Prefix: | aa_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Civil settlement amount and legal cost. + References No definition available. + Details
Name: | aa_CivilSettlementAmountAndLegalCost
Namespace Prefix: | aa_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Damages awarded to plaintiff, pre-judgment interest. + References No definition available. + Details
Name: | aa_DamagesAwardedToPlaintiffPreJudgmentInterest
Namespace Prefix: | aa_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Due from third parties. + References No definition available. + Details
Name: | aa_DueFromThirdParties
Namespace Prefix: | aa_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Effective date of settlement under agreement. + References No definition available. + Details
Name: | aa_EffectiveDateOfSettlementUnderAgreement
Namespace Prefix: | aa_
Data Type: | xbrli:dateItemType
Balance Type: | na
Period Type: | duration

X
- Definition Establishment reserves. + References No definition available. + Details
Name: | aa_EstablishmentReserves
Namespace Prefix: | aa_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Government investigation cost and legal charges. + References No definition available. + Details
Name: | aa_GovernmentInvestigationCostAndLegalCharges
Namespace Prefix: | aa_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Litigation settlement expenses charged on investigations. + References No definition available. + Details
Name: | aa_LitigationSettlementExpensesChargedOnInvestigations
Namespace Prefix: | aa_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Litigation settlement number of annual installments of payment. + References No definition available. + Details
Name: | aa_LitigationSettlementNumberOfAnnualInstallmentsOfPayment
Namespace Prefix: | aa_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Litigation settlement number of annual installments of payment including fine. + References No definition available. + Details
Name: | aa_LitigationSettlementNumberOfAnnualInstallmentsOfPaymentIncludingFine
Namespace Prefix: | aa_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Litigation settlement number of installments. + References No definition available. + Details
Name: | aa_LitigationSettlementNumberOfInstallments
Namespace Prefix: | aa_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Litigation settlement number of years identified for installments payable. + References No definition available. + Details
Name: | aa_LitigationSettlementNumberOfYearsIdentifiedForInstallmentsPayable
Namespace Prefix: | aa_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Litigation settlement rejected amount. + References No definition available. + Details
Name: | aa_LitigationSettlementRejectedAmount
Namespace Prefix: | aa_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Loss contingency, recovery from third party. + References No definition available. + Details
Name: | aa_LossContingencyRecoveryFromThirdParty
Namespace Prefix: | aa_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Loss contingency settlement agreement amount. + References No definition available. + Details
Name: | aa_LossContingencySettlementAgreementAmount
Namespace Prefix: | aa_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Loss contingency settlement agreement amount of fine. + References No definition available. + Details
Name: | aa_LossContingencySettlementAgreementAmountOfFine
Namespace Prefix: | aa_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Loss contingency settlement agreement amount of installment payable due in year five. + References No definition available. + Details
Name: | aa_LossContingencySettlementAgreementAmountOfInstallmentPayableDueInYearFive
Namespace Prefix: | aa_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Loss contingency settlement agreement amount of installment payable due in year four. + References No definition available. + Details
Name: | aa_LossContingencySettlementAgreementAmountOfInstallmentPayableDueInYearFour
Namespace Prefix: | aa_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Loss contingency settlement agreement amount of installment payable due in year three. + References No definition available. + Details
Name: | aa_LossContingencySettlementAgreementAmountOfInstallmentPayableDueInYearThree
Namespace Prefix: | aa_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Loss contingency settlement agreement amount of installment payable due in year two. + References No definition available. + Details
Name: | aa_LossContingencySettlementAgreementAmountOfInstallmentPayableDueInYearTwo
Namespace Prefix: | aa_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Loss contingency settlement agreement amount of one time administrative forfeiture. + References No definition available. + Details
Name: | aa_LossContingencySettlementAgreementAmountOfOneTimeAdministrativeForfeiture
Namespace Prefix: | aa_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Loss contingency settlement agreement amount payable due in next twelve months. + References No definition available. + Details
Name: | aa_LossContingencySettlementAgreementAmountPayableDueInNextTwelveMonths
Namespace Prefix: | aa_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Loss contingency settlement agreement consideration amount. + References No definition available. + Details
Name: | aa_LossContingencySettlementAgreementConsiderationAmount
Namespace Prefix: | aa_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Loss contingency settlement amount. + References No definition available. + Details
Name: | aa_LossContingencySettlementAmount
Namespace Prefix: | aa_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Number of affiliated operating entities. + References No definition available. + Details
Name: | aa_NumberOfAffiliatedOperatingEntities
Namespace Prefix: | aa_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Number of installments. + References No definition available. + Details
Name: | aa_NumberOfInstallments
Namespace Prefix: | aa_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Number of plants. + References No definition available. + Details
Name: | aa_NumberOfPlants
Namespace Prefix: | aa_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Number of years identified for installments payable. + References No definition available. + Details
Name: | aa_NumberOfYearsIdentifiedForInstallmentsPayable
Namespace Prefix: | aa_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Year operating under a power supply structured. + References No definition available. + Details
Name: | aa_NumberOfYearsOperatingUnderPowerSupplyStructured
Namespace Prefix: | aa_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Payment for litigation settlement installment amount. + References No definition available. + Details
Name: | aa_PaymentForLitigationSettlementInstallmentAmount
Namespace Prefix: | aa_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Percentage owned in affiliated operating entities. + References No definition available. + Details
Name: | aa_PercentageOwnedInAffiliatedOperatingEntities
Namespace Prefix: | aa_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Period of alleged conspiracy, years. + References No definition available. + Details
Name: | aa_PeriodOfAllegedConspiracyYears
Namespace Prefix: | aa_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Retired former employees involved in class action. + References No definition available. + Details
Name: | aa_RetiredFormerEmployeesInvolvedInClassAction
Namespace Prefix: | aa_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Settlement expense allocation percentage. + References No definition available. + Details
Name: | aa_SettlementExpenseAllocationPercentage
Namespace Prefix: | aa_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Settlement expense allocation percentage on reaching investigation to certain authority. + References No definition available. + Details
Name: | aa_SettlementExpenseAllocationPercentageOnReachingInvestigationToCertainAuthority
Namespace Prefix: | aa_
Data Type: | num:percentItemType
Balance Type: | na
Period Type: | duration

X
- Definition Trial length, number of days. + References No definition available. + Details
Name: | aa_TrialLengthNumberOfDays
Namespace Prefix: | aa_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Write-off of receivable. + References No definition available. + Details
Name: | aa_WriteOffOfReceivable
Namespace Prefix: | aa_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition The amount of expense provided in the period for legal costs incurred on or before the balance sheet date pertaining to resolved, pending or threatened litigation, including arbitration and mediation proceedings. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 225 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SX 210.5-03.3) -URI http://asc.fasb.org/extlink&oid=26872669&loc=d3e20235-122688 + Details
Name: | us-gaap_LegalFees
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Aggregate carrying amount of the estimated litigation liability for known or estimated probable loss from litigation, which may include attorneys' fees and other litigation costs. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14326-108349 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.25) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
Name: | us-gaap_LitigationReserve
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of litigation expense, including but not limited to legal, forensic, accounting, and investigative fees. + References No definition available. + Details
Name: | us-gaap_LitigationSettlementExpense
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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

X
- Definition Amount of damages awarded to the plaintiff in the legal matter. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14326-108349 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section 50 -Paragraph 4 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14435-108349 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section 50 -Paragraph 9 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14557-108349 + Details
Name: | us-gaap_LossContingencyDamagesAwardedValue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition The value (monetary amount) of the award the plaintiff seeks in the legal matter. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14326-108349 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section 50 -Paragraph 4 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14435-108349 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section 50 -Paragraph 9 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14557-108349 + Details
Name: | us-gaap_LossContingencyDamagesSoughtValue
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Reflects the estimated amount of loss from the specified contingency as of the balance sheet date. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section 50 -Paragraph 4 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14435-108349 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section 50 -Paragraph 9 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14557-108349 + Details
Name: | us-gaap_LossContingencyEstimateOfPossibleLoss
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition The estimated maximum amount of possible loss from the contingency. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section 50 -Paragraph 4 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14435-108349 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section 50 -Paragraph 9 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14557-108349 + Details
Name: | us-gaap_LossContingencyRangeOfPossibleLossMaximum
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition The estimated minimum amount of possible loss from the contingency. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section 50 -Paragraph 4 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14435-108349 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section 50 -Paragraph 9 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14557-108349 + Details
Name: | us-gaap_LossContingencyRangeOfPossibleLossMinimum
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of receivable related to a loss contingency accrual. For example, an insurance recovery receivable. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 460 -SubTopic 10 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=6851643&loc=d3e12053-110248 + Details
Name: | us-gaap_LossContingencyReceivable
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Description of the terms of a settlement agreement which resolved the legal matter, including the nature of the consideration, timing of payment, and the nature of rights obtained or lost (for example, but not limited to, patent, trademark, copyright, license and franchise rights). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14326-108349 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section 50 -Paragraph 4 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14435-108349 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 450 -SubTopic 20 -Section 50 -Paragraph 9 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=25496072&loc=d3e14557-108349 + Details
Name: | us-gaap_LossContingencySettlementAgreementTerms
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition The amount of cash paid for the settlement of litigation or for other legal issues during the period. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 25 -Subparagraph (g) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3536-108585 + Details
Name: | us-gaap_PaymentsForLegalSettlements
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition Cumulative provision for contract losses not offset against related costs accumulated on the balance sheet. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 605 -SubTopic 35 -Section 45 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=6802688&loc=d3e57777-111642 + Details
Name: | us-gaap_ProvisionForLossOnContracts
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

X
- Definition Amount of expenses associated with exit or disposal activities pursuant to an authorized plan. Excludes expenses related to a discontinued operation or an asset retirement obligation. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 28 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 420 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=6394359&loc=d3e17939-110869 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 420 -SubTopic 10 -Section S99 -Paragraph 2 -Subparagraph (SAB TOPIC 5.P.4(b)) -URI http://asc.fasb.org/extlink&oid=27011515&loc=d3e140904-122747 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 420 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SAB TOPIC 5.P.3) -URI http://asc.fasb.org/extlink&oid=27011515&loc=d3e140864-122747 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Staff Accounting Bulletin (SAB) -Number Topic 5 -Section P -Subsection 3, 4 + Details
Name: | us-gaap_RestructuringCharges
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration