Properties, Plants, and Equipment, Net - Schedule of Properties, Plants, and Equipment, Net (Detail) - USD ($) $ in Millions	Dec. 31, 2015	Dec. 31, 2014
Property, Plant and Equipment [Line Items]
Properties, plants, and equipment, gross	$ 32,382	$ 34,051
Less: accumulated depreciation, depletion, and amortization	18,872	19,091
Properties, plants, and equipment excluding construction work-in-progress	13,510	14,960
Construction work-in-progress	1,305	1,466
Properties, plants, and equipment, net	14,815	16,426
Land and Land Rights, Including Mines [Member]
Property, Plant and Equipment [Line Items]
Properties, plants, and equipment, gross	481	548
Structures [Member]
Property, Plant and Equipment [Line Items]
Properties, plants, and equipment, gross	10,340	11,300
Machinery and Equipment [Member]
Property, Plant and Equipment [Line Items]
Properties, plants, and equipment, gross	21,561	22,203
Operating Segments [Member] | Alumina [Member] | Alumina Refining [Member] | Structures [Member]
Property, Plant and Equipment [Line Items]
Properties, plants, and equipment, gross	2,387	2,750
Operating Segments [Member] | Alumina [Member] | Alumina Refining [Member] | Machinery and Equipment [Member]
Property, Plant and Equipment [Line Items]
Properties, plants, and equipment, gross	3,709	4,165
Operating Segments [Member] | Alumina [Member] | Bauxite Mining [Member] | Structures [Member]
Property, Plant and Equipment [Line Items]
Properties, plants, and equipment, gross	1,054	1,403
Operating Segments [Member] | Alumina [Member] | Bauxite Mining [Member] | Machinery and Equipment [Member]
Property, Plant and Equipment [Line Items]
Properties, plants, and equipment, gross	428	524
Operating Segments [Member] | Primary Metals [Member] | Aluminum Smelting [Member] | Structures [Member]
Property, Plant and Equipment [Line Items]
Properties, plants, and equipment, gross	3,567	3,725
Operating Segments [Member] | Primary Metals [Member] | Aluminum Smelting [Member] | Machinery and Equipment [Member]
Property, Plant and Equipment [Line Items]
Properties, plants, and equipment, gross	6,831	7,210
Operating Segments [Member] | Primary Metals [Member] | Power Generation [Member] | Structures [Member]
Property, Plant and Equipment [Line Items]
Properties, plants, and equipment, gross	518	645
Operating Segments [Member] | Primary Metals [Member] | Power Generation [Member] | Machinery and Equipment [Member]
Property, Plant and Equipment [Line Items]
Properties, plants, and equipment, gross	1,044	1,080
Operating Segments [Member] | Global Rolled Products [Member] | Structures [Member]
Property, Plant and Equipment [Line Items]
Properties, plants, and equipment, gross	1,298	1,276
Operating Segments [Member] | Global Rolled Products [Member] | Machinery and Equipment [Member]
Property, Plant and Equipment [Line Items]
Properties, plants, and equipment, gross	5,372	5,333
Operating Segments [Member] | Engineered Products and Solutions [Member] | Structures [Member]
Property, Plant and Equipment [Line Items]
Properties, plants, and equipment, gross	658	547
Operating Segments [Member] | Engineered Products and Solutions [Member] | Machinery and Equipment [Member]
Property, Plant and Equipment [Line Items]
Properties, plants, and equipment, gross	2,745	2,402
Operating Segments [Member] | Transportation and Construction Solutions [Member] | Structures [Member]
Property, Plant and Equipment [Line Items]
Properties, plants, and equipment, gross	239	239
Operating Segments [Member] | Transportation and Construction Solutions [Member] | Machinery and Equipment [Member]
Property, Plant and Equipment [Line Items]
Properties, plants, and equipment, gross	682	669
Other [Member]
Property, Plant and Equipment [Line Items]
Properties, plants, and equipment, net	733	819
Other [Member] | Structures [Member]
Property, Plant and Equipment [Line Items]
Properties, plants, and equipment, gross	619	715
Other [Member] | Machinery and Equipment [Member]
Property, Plant and Equipment [Line Items]
Properties, plants, and equipment, gross	$ 750	$ 820