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Derivatives And Other Financial Instruments (Schedule Of Quantitative Information For Level 3 Derivative Contracts) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2012
Discounted Cash Flow [Member] | Embedded Credit Derivative [Member]
Derivatives And Other Financial Instruments [Line Items]
Percentage of credit spread	1.83%
Maximum [Member] | Discounted Cash Flow [Member] | Aluminum Contracts [Member]
Derivatives And Other Financial Instruments [Line Items]
Price of aluminum beyond forward curve	3,057
Maturity data of aluminum beyond forward curve	2027
Expected future aluminum prices	2,605
Expected future oil prices	120
Maximum [Member] | Discounted Cash Flow [Member] | Embedded Credit Derivative [Member]
Derivatives And Other Financial Instruments [Line Items]
Percentage of credit spread	2.02%
Maximum [Member] | Discounted Cash Flow [Member] | Energy Contracts [Member]
Derivatives And Other Financial Instruments [Line Items]
Price of electricity beyond forward curve	172
Maturity date of electricity beyond forward curve	2036
Minimum [Member] | Discounted Cash Flow [Member] | Aluminum Contracts [Member]
Derivatives And Other Financial Instruments [Line Items]
Price of aluminum beyond forward curve	2,793
Maturity data of aluminum beyond forward curve	2022
Expected future aluminum prices	2,152
Expected future oil prices	91
Minimum [Member] | Discounted Cash Flow [Member] | Embedded Credit Derivative [Member]
Derivatives And Other Financial Instruments [Line Items]
Percentage of credit spread	1.64%
Minimum [Member] | Discounted Cash Flow [Member] | Energy Contracts [Member]
Derivatives And Other Financial Instruments [Line Items]
Price of electricity beyond forward curve	48
Maturity date of electricity beyond forward curve	2012
Interrelationship Of Future Aluminum And Oil Prices [Member] | Aluminum Contracts [Member]
Derivatives And Other Financial Instruments [Line Items]
Derivative Assets, Fair Value	4
Price Of Aluminum Beyond Forward Curve [Member] | Aluminum Contracts [Member]
Derivatives And Other Financial Instruments [Line Items]
Derivative Liabilities, Fair Value	670
Price Of Electricity Beyond Forward Curve [Member] | Energy Contracts [Member]
Derivatives And Other Financial Instruments [Line Items]
Derivative Liabilities, Fair Value	10
Credit Spread Between Alcoa And Counterparty [Member] | Embedded Credit Derivative [Member]
Derivatives And Other Financial Instruments [Line Items]
Derivative Liabilities, Fair Value	28

X

- Definition

Average percentage of credit spread.

+ References

No definition available.

+ Details

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Namespace Prefix:	aa_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

X

- Details

Name:	aa_DerivativesAndOtherFinancialInstrumentsLineItems
Namespace Prefix:	aa_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Expected future aluminum prices.

+ References

No definition available.

+ Details

Name:	aa_ExpectedFutureAluminumPrices
Namespace Prefix:	aa_
Data Type:	us-types:perUnitItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Expected future oil prices.

+ References

No definition available.

+ Details

Name:	aa_ExpectedFutureOilPrices
Namespace Prefix:	aa_
Data Type:	us-types:perUnitItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Expected price of aluminum through forward curve

+ References

No definition available.

+ Details

Name:	aa_ExpectedPriceOfAluminumThroughForwardCurve
Namespace Prefix:	aa_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

X

- Definition

Maturity data of aluminum beyond forward curve.

+ References

No definition available.

+ Details

Name:	aa_MaturityDataOfAluminumBeyondForwardCurve
Namespace Prefix:	aa_
Data Type:	xbrli:gYearItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Maturity date of electricity beyond forward curve.

+ References

No definition available.

+ Details

Name:	aa_MaturityDateOfElectricityBeyondForwardCurve
Namespace Prefix:	aa_
Data Type:	xbrli:gYearItemType
Balance Type:	na
Period Type:	duration

X

- Definition

Price of electricity through forward curve.

+ References

No definition available.

+ Details

Name:	aa_PriceOfElectricityThroughForwardCurve
Namespace Prefix:	aa_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

X

- Definition

Fair value as of the balance sheet date of the gross assets less the gross liabilities of a derivative asset or group of derivative assets.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 825

-SubTopic 10

-Section 50

-Paragraph 15

-URI http://asc.fasb.org/extlink&oid=6947722&loc=d3e13495-108611



Reference 2: 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



Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 45

-Paragraph 6

-URI http://asc.fasb.org/extlink&oid=6945355&loc=d3e41271-113958



Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 825

-SubTopic 10

-Section 50

-Paragraph 10

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=6947722&loc=d3e13433-108611

+ Details

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

X

- Definition

Fair value as of the balance sheet date of the gross assets less the gross liabilities of a derivative liability or group of derivative liabilities.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 825

-SubTopic 10

-Section 50

-Paragraph 15

-URI http://asc.fasb.org/extlink&oid=6947722&loc=d3e13495-108611



Reference 2: 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



Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 45

-Paragraph 6

-URI http://asc.fasb.org/extlink&oid=6945355&loc=d3e41271-113958



Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 825

-SubTopic 10

-Section 50

-Paragraph 10

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=6947722&loc=d3e13433-108611

+ Details

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