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Cash Flow Information - Schedule of Cash Paid for Acquisitions (Detail) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010
Schedule Of Summary Of Acquisitions Of Properties [Line Items]
Assets acquired	$ 253	$ 87
Liabilities assumed	(12)	(15)
Noncontrolling interests acquired		4
Redemption of convertible securities of subsidiary		40
Reduction in Alcoa shareholders' equity		22
Cash paid	241	138
Less: cash acquired	1
Net cash paid	$ 240	$ 138

X

- Definition

Business Acquisition, Cost Of Acquired Entity, Reduction In Shareholders' Equity

+ References

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- Definition

Payments for acquisitions net of cash acquired

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- Definition

Redemption Of Convertible Securities Of Subsidiary

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X

- Definition

Amount of cash paid to acquire the entity.

+ References

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-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 141R

-Paragraph 68

-Subparagraph f(1)

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.



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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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- Definition

The amount of acquisition cost of a business combination allocated to assets acquired.

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-Name Statement of Financial Accounting Standard (FAS)

-Number 141

-Paragraph 37

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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- Definition

The amount of acquisition cost of a business combination allocated to liabilities assumed.

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-Publisher FASB

-Name Emerging Issues Task Force (EITF)

-Number 98-1

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.



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-Name Statement of Financial Accounting Standard (FAS)

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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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- Definition

This element represents the fair value of the noncontrolling interest in the acquiree at the acquisition date.

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- Definition

The cash inflow associated with the acquisition of business during the period (for example, cash that was held by the acquired business).

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

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Investing Activities

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