Properties, Plants, and Equipment, Net - Schedule of Properties, Plants, and Equipment, Net (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Property, Plant and Equipment [Line Items]
Properties, plants, and equipment, gross	$ 34,051us-gaap_PropertyPlantAndEquipmentGross	$ 35,299us-gaap_PropertyPlantAndEquipmentGross
Less: accumulated depreciation, depletion, and amortization	19,091	19,227
Properties, plants, and equipment excluding construction work-in-progress	14,960	16,072
Construction work-in-progress	1,466us-gaap_ConstructionInProgressGross	1,567us-gaap_ConstructionInProgressGross
Properties, plants, and equipment, net	16,426us-gaap_PropertyPlantAndEquipmentNet	17,639us-gaap_PropertyPlantAndEquipmentNet
Land and Land Rights, Including Mines [Member]
Property, Plant and Equipment [Line Items]
Properties, plants, and equipment, gross	548	639
Structures [Member]
Property, Plant and Equipment [Line Items]
Properties, plants, and equipment, gross	11,300	11,890
Machinery and Equipment [Member]
Property, Plant and Equipment [Line Items]
Properties, plants, and equipment, gross	22,203	22,770
Operating Segments [Member] \| Alumina [Member] \| Alumina Refining [Member] \| Structures [Member]
Property, Plant and Equipment [Line Items]
Properties, plants, and equipment, gross	2,750	3,049
Operating Segments [Member] \| Alumina [Member] \| Alumina Refining [Member] \| Machinery and Equipment [Member]
Property, Plant and Equipment [Line Items]
Properties, plants, and equipment, gross	4,165	4,685
Operating Segments [Member] \| Alumina [Member] \| Bauxite Mining [Member] \| Structures [Member]
Property, Plant and Equipment [Line Items]
Properties, plants, and equipment, gross	1,403	1,591
Operating Segments [Member] \| Alumina [Member] \| Bauxite Mining [Member] \| Machinery and Equipment [Member]
Property, Plant and Equipment [Line Items]
Properties, plants, and equipment, gross	524	596
Operating Segments [Member] \| Primary Metals [Member] \| Aluminum Smelting [Member] \| Structures [Member]
Property, Plant and Equipment [Line Items]
Properties, plants, and equipment, gross	3,725	3,863
Operating Segments [Member] \| Primary Metals [Member] \| Aluminum Smelting [Member] \| Machinery and Equipment [Member]
Property, Plant and Equipment [Line Items]
Properties, plants, and equipment, gross	7,210	7,674
Operating Segments [Member] \| Primary Metals [Member] \| Power Generation [Member] \| Structures [Member]
Property, Plant and Equipment [Line Items]
Properties, plants, and equipment, gross	645	683
Operating Segments [Member] \| Primary Metals [Member] \| Power Generation [Member] \| Machinery and Equipment [Member]
Property, Plant and Equipment [Line Items]
Properties, plants, and equipment, gross	1,080	1,101
Operating Segments [Member] \| Global Rolled Products [Member] \| Structures [Member]
Property, Plant and Equipment [Line Items]
Properties, plants, and equipment, gross	1,276	1,256
Operating Segments [Member] \| Global Rolled Products [Member] \| Machinery and Equipment [Member]
Property, Plant and Equipment [Line Items]
Properties, plants, and equipment, gross	5,333	5,374
Operating Segments [Member] \| Engineered Products and Solutions [Member] \| Structures [Member]
Property, Plant and Equipment [Line Items]
Properties, plants, and equipment, gross	786	693
Operating Segments [Member] \| Engineered Products and Solutions [Member] \| Machinery and Equipment [Member]
Property, Plant and Equipment [Line Items]
Properties, plants, and equipment, gross	3,071	2,481
Other [Member]
Property, Plant and Equipment [Line Items]
Properties, plants, and equipment, net	819	879
Other [Member] \| Structures [Member]
Property, Plant and Equipment [Line Items]
Properties, plants, and equipment, gross	715	755
Other [Member] \| Machinery and Equipment [Member]
Property, Plant and Equipment [Line Items]
Properties, plants, and equipment, gross	$ 820	$ 859

Properties plants and equipment excluding construction work in progress.

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- Definition

Amount of accumulated depreciation, depletion and amortization for physical assets used in the normal conduct of business to produce goods and services.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 360

-SubTopic 10

-Section 50

-Paragraph 1

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-Name Accounting Standards Codification

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Amount of structure or a modification to a structure under construction. Includes recently completed structures or modifications to structures that have not been placed into service.

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+ References

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

-Publisher FASB

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Amount after accumulated depreciation, depletion and amortization of physical assets used in the normal conduct of business to produce goods and services and not intended for resale. Examples include, but are not limited to, land, buildings, machinery and equipment, office equipment, and furniture and fixtures.

+ References

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

-Publisher FASB

-Name Accounting Standards Codification

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-SubTopic 10

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-URI http://asc.fasb.org/extlink&oid=6391035&loc=d3e2868-110229

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