Cash equivalents maximum maturity period of highly liquid investments.

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- Definition

Discontinued operations businesses expected to be disposed within certain years.

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- Definition

Goodwill impairment loss attributable to parent.

+ References

No definition available.

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- Definition

Implied fair value of goodwill during second step impairment analysis.

+ References

No definition available.

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- Definition

Maximum hedging contracts period.

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No definition available.

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- Definition

Minimum number of reporting units being subjected for goodwill impairment test.

+ References

No definition available.

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- Definition

Minimum percentage of estimated fair value of reporting unit to be less than carrying amount of goodwill.

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No definition available.

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- Definition

Mining period.

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No definition available.

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- Definition

Number of reporting units being subjected to goodwill impairment test.

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No definition available.

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- Definition

Number of reporting units for goodwill allocation.

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No definition available.

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- Definition

Number of reporting units tested for goodwill impairment.

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No definition available.

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- Definition

Percentage of total goodwill allocated to reporting units.

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No definition available.

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- Definition

The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 323

-SubTopic 10

-Section 50

-Paragraph 3

-Subparagraph (a)(1)

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- Definition

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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

-Publisher FASB

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-Topic 350

-SubTopic 20

-Section 50

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- Definition

Amount of loss from the write-down of an asset representing the future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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- Definition

Number of reporting units tested for impairment of goodwill. A reporting unit is an operating segment or one level below an operating segment.

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

-Publisher FASB

-Name Accounting Standards Codification

-Glossary Reporting Unit

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Summary of Significant Accounting Policies - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	3 Months Ended	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2014 Reporting_Unit	Dec. 31, 2013	Dec. 31, 2012	Nov. 14, 2014
Summary Of Significant Accounting Policies [Line Items]
Percent of equity investments in other entity		40.00%
Original maturity of cash equivalents		3 months
Number of reporting units being subjected to goodwill impairment test		9
Segment Allocation, Goodwill Recognized	$ 3,415us-gaap_Goodwill	$ 5,247us-gaap_Goodwill	$ 3,415us-gaap_Goodwill	$ 5,170us-gaap_Goodwill
Minimum percentage of estimated fair value of reporting unit to be less than carrying amount of goodwill		50.00%
Minimum number of reporting units being subjected for goodwill impairment test		3
Qualitative assessment for reporting units		5
Goodwill impairment	1,731us-gaap_GoodwillImpairmentLoss		1,731us-gaap_GoodwillImpairmentLoss
Goodwill impairment after noncontrolling interest	1,719
Maximum hedging contracts period, in years		5 years
Businesses expected to be disposed within, years		1 year
Engineered Products and Solutions [Member]
Summary Of Significant Accounting Policies [Line Items]
Number of reporting units		5
Segment Allocation, Goodwill Recognized	2,670	4,519	2,670	2,677	1,898
Number of reporting units for goodwill allocation		2
Qualitative assessment for reporting units		4
Other Operating Segments [Member]
Summary Of Significant Accounting Policies [Line Items]
Number of reporting units		4
Primary Metals [Member]
Summary Of Significant Accounting Policies [Line Items]
Segment Allocation, Goodwill Recognized	0		0	997
Implied fair value of goodwill			0
Goodwill impairment	1,731		989
Goodwill impairment after noncontrolling interest	1,719		1,719
Alcoa Fastening Systems [Member] \| Engineered Products and Solutions [Member]
Summary Of Significant Accounting Policies [Line Items]
Segment Allocation, Goodwill Recognized		1,145
Alcoa Power and Propulsion [Member] \| Engineered Products and Solutions [Member]
Summary Of Significant Accounting Policies [Line Items]
Segment Allocation, Goodwill Recognized		$ 1,590
Maximum [Member]
Summary Of Significant Accounting Policies [Line Items]
Percent of equity investments in other entity		50.00%
Maximum [Member] \| Bauxite Mining [Member]
Summary Of Significant Accounting Policies [Line Items]
Period of mining		5 years
Minimum [Member] \| Engineered Products and Solutions [Member]
Summary Of Significant Accounting Policies [Line Items]
Percentage of total goodwill allocated to reporting units		80.00%
Minimum [Member] \| Bauxite Mining [Member]
Summary Of Significant Accounting Policies [Line Items]
Period of mining		1 year