Properties, Plants, and Equipment, Net - Schedule of Properties, Plants, and Equipment, Net (Detail) (USD $) In Millions, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Property, Plant and Equipment [Line Items]
Land and land rights, including mines	$ 676	$ 665
Structures	12,198	12,060
Machinery and equipment	23,509	23,237
Properties, plants, and equipment, gross	36,383	35,962
Less: accumulated depreciation, depletion, and amortization	19,190	18,326
Properties, plants, and equipment excluding construction work-in-progress	17,193	17,636
Construction work-in-progress	1,754	1,646
Properties, plants, and equipment, net	18,947	19,282
Global Rolled Products [Member]
Property, Plant and Equipment [Line Items]
Structures	1,232	1,204
Machinery and equipment	5,174	5,059
Engineered Products and Solutions [Member]
Property, Plant and Equipment [Line Items]
Structures	678	648
Machinery and equipment	2,415	2,252
Other [Member]
Property, Plant and Equipment [Line Items]
Structures	760	714
Machinery and equipment	883	764
Alumina [Member] | Alumina refining [Member]
Property, Plant and Equipment [Line Items]
Structures	3,319	3,280
Machinery and equipment	5,279	5,223
Alumina [Member] | Bauxite mining [Member]
Property, Plant and Equipment [Line Items]
Structures	1,563	1,597
Machinery and equipment	650	661
Primary Metals [Member] | Aluminum smelting [Member]
Property, Plant and Equipment [Line Items]
Structures	4,042	3,950
Machinery and equipment	8,114	8,266
Primary Metals [Member] | Power generation [Member]
Property, Plant and Equipment [Line Items]
Structures	604	667
Machinery and equipment	$ 994	$ 1,012