XML 134 R150.htm IDEA: XBRL DOCUMENT v2.4.1.9

Derivatives and Other Financial Instruments - Schedule of Net Fair Values of Level 3 Derivative Instruments and Effect of Hypothetical Change (Increase or Decrease of 10%) in Market Prices or Rates (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014
Embedded Aluminum Derivative [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Fair value asset/(liability)	$ (110)us-gaap_DerivativeAssetsLiabilitiesAtFairValueNet / us-gaap_DerivativeInstrumentRiskAxis = aa_EmbeddedAluminumDerivativeMember
Index change of + / - 10%	413aa_IndexChangeOfPlusOrMinusTenPercentInMarketPriceOrRate / us-gaap_DerivativeInstrumentRiskAxis = aa_EmbeddedAluminumDerivativeMember
Embedded Credit Derivative [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Fair value asset/(liability)	(18)us-gaap_DerivativeAssetsLiabilitiesAtFairValueNet / us-gaap_DerivativeInstrumentRiskAxis = aa_EmbeddedCreditDerivativeMember
Index change of + / - 10%	2aa_IndexChangeOfPlusOrMinusTenPercentInMarketPriceOrRate / us-gaap_DerivativeInstrumentRiskAxis = aa_EmbeddedCreditDerivativeMember
Energy Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Fair value asset/(liability)	2us-gaap_DerivativeAssetsLiabilitiesAtFairValueNet / us-gaap_DerivativeInstrumentRiskAxis = aa_EnergyContractsMember
Index change of + / - 10%	$ 180aa_IndexChangeOfPlusOrMinusTenPercentInMarketPriceOrRate / us-gaap_DerivativeInstrumentRiskAxis = aa_EnergyContractsMember

X

- Definition

Index change of plus or minus ten percent in market price or rate.

+ References

No definition available.

+ Details

Name:	aa_IndexChangeOfPlusOrMinusTenPercentInMarketPriceOrRate
Namespace Prefix:	aa_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Definition

Fair values as of the balance sheet date of the net amount of all assets and liabilities resulting from contracts that meet the criteria of being accounted for as derivative instruments.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 45

-Paragraph 5

-URI http://asc.fasb.org/extlink&oid=6945355&loc=d3e41228-113958

+ Details

Name:	us-gaap_DerivativeAssetsLiabilitiesAtFairValueNet
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Details

Name:	us-gaap_DerivativeInstrumentsGainLossLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=aa_EmbeddedAluminumDerivativeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=aa_EmbeddedCreditDerivativeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_DerivativeInstrumentRiskAxis=aa_EnergyContractsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: