XML 22 R56.htm IDEA: XBRL DOCUMENT
v2.4.1.9

Subsequent Events - Additional Information (Detail) (USD $) In Millions, unless otherwise specified | 1 Months Ended | 3 Months Ended | 0 Months Ended
--- | --- | --- | ---
Jun. 12, 2012 Installment | Mar. 31, 2015 | Apr. 08, 2015 Installment Refinery
Subsequent Event [Line Items] |  |  |
Number of installments | 5 aa_NumberOfInstallments |  |
Alcoa Of Australia Limited [Member] | Majority-Owned Subsidiary | Service Agreements [Member] |  |  |
Subsequent Event [Line Items] |  |  |
Gas supply agreement period |  | 12 years |
Subsequent Event [Member] | Alcoa Of Australia Limited [Member] | Majority-Owned Subsidiary | Service Agreements [Member] |  |  |
Subsequent Event [Line Items] |  |  |
Number of alumina refineries to be powered under supplied agreement |  |  | 3 aa_NumberOfRefineries / us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis = us-gaap_ServiceAgreementsMember / dei_LegalEntityAxis = us-gaap_SubsidiariesMember / us-gaap_OtherOwnershipInterestsByNameAxis = aa_AlcoaOfAustraliaLimitedMember / us-gaap_SubsequentEventTypeAxis = us-gaap_SubsequentEventMember
Number of installments |  |  | 2 aa_NumberOfInstallments / us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis = us-gaap_ServiceAgreementsMember / dei_LegalEntityAxis = us-gaap_SubsidiariesMember / us-gaap_OtherOwnershipInterestsByNameAxis = aa_AlcoaOfAustraliaLimitedMember / us-gaap_SubsequentEventTypeAxis = us-gaap_SubsequentEventMember
Contract termination penalty |  |  | $ 0 us-gaap_LossOnContractTerminationForDefault / us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis = us-gaap_ServiceAgreementsMember / dei_LegalEntityAxis = us-gaap_SubsidiariesMember / us-gaap_OtherOwnershipInterestsByNameAxis = aa_AlcoaOfAustraliaLimitedMember / us-gaap_SubsequentEventTypeAxis = us-gaap_SubsequentEventMember
First installment paid at the time of third party obligation |  |  | 500 us-gaap_ContractualObligation / us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis = us-gaap_ServiceAgreementsMember / dei_LegalEntityAxis = us-gaap_SubsidiariesMember / us-gaap_OtherOwnershipInterestsByNameAxis = aa_AlcoaOfAustraliaLimitedMember / us-gaap_SubsequentEventTypeAxis = us-gaap_SubsequentEventMember
Subsequent Event [Member] | Alcoa Of Australia Limited [Member] | Majority-Owned Subsidiary | Service Agreements [Member] | First Installment [Member] |  |  |
Subsequent Event [Line Items] |  |  |
First installment paid at the time of third party obligation |  |  | 300 us-gaap_ContractualObligation / us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis = us-gaap_ServiceAgreementsMember / dei_LegalEntityAxis = us-gaap_SubsidiariesMember / us-gaap_OtherCommitmentsAxis = aa_FirstInstallementMember / us-gaap_OtherOwnershipInterestsByNameAxis = aa_AlcoaOfAustraliaLimitedMember / us-gaap_SubsequentEventTypeAxis = us-gaap_SubsequentEventMember
Subsequent Event [Member] | Alcoa Of Australia Limited [Member] | Majority-Owned Subsidiary | Service Agreements [Member] | Second Installment [Member] |  |  |
Subsequent Event [Line Items] |  |  |
First installment paid at the time of third party obligation |  |  | $ 200 us-gaap_ContractualObligation / us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis = us-gaap_ServiceAgreementsMember / dei_LegalEntityAxis = us-gaap_SubsidiariesMember / us-gaap_OtherCommitmentsAxis = aa_SecondInstallmentMember / us-gaap_OtherOwnershipInterestsByNameAxis = aa_AlcoaOfAustraliaLimitedMember / us-gaap_SubsequentEventTypeAxis = us-gaap_SubsequentEventMember

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- 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

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- Definition Number Of Refineries + References No definition available. + Details
Name: | aa_NumberOfRefineries
Namespace Prefix: | aa_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

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- Definition Amount of contractual obligation, including but not limited to, long-term debt, capital lease obligations, operating lease obligations, purchase obligations, and other commitments. + References No definition available. + Details
Name: | us-gaap_ContractualObligation
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | instant

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- Definition Period covered by the long-term purchase commitment, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. + References No definition available. + Details
Name: | us-gaap_LongtermPurchaseCommitmentPeriod
Namespace Prefix: | us-gaap_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

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- Definition The amount of the loss on termination of a contract for default. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 912 -SubTopic 20 -Section 45 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=6539154&loc=d3e52595-109384 + Details
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Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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- Details
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Namespace Prefix: | us-gaap_
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Period Type: | duration

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- Details
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Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

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- Details
Name: | us-gaap_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |