Properties, Plants, and Equipment, Net - Schedule of Properties, Plants, and Equipment, Net (Detail) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Property, Plant and Equipment [Line Items]
Less: accumulated depreciation, depletion, and amortization	$ 13,130	$ 13,332
Properties, plants, and equipment excluding construction work-in-progress	6,335	6,855
Construction work-in-progress	288	335
Properties, plants, and equipment, net	6,623	7,190
Land [Member]
Property, Plant and Equipment [Line Items]
Properties, plants, and equipment, gross	264	320
Structures [Member]
Property, Plant and Equipment [Line Items]
Properties, plants, and equipment, gross	7,525	7,750
Machinery and Equipment [Member]
Property, Plant and Equipment [Line Items]
Properties, plants, and equipment, gross	11,676	12,117
Property Plant And Equipment Other Than Construction In Progress [Member]
Property, Plant and Equipment [Line Items]
Properties, plants, and equipment, gross	19,465	20,187
Operating Segments [Member] | Bauxite Mining [Member] | Structures [Member]
Property, Plant and Equipment [Line Items]
Properties, plants, and equipment, gross	1,148	1,119
Operating Segments [Member] | Bauxite Mining [Member] | Machinery and Equipment [Member]
Property, Plant and Equipment [Line Items]
Properties, plants, and equipment, gross	565	517
Operating Segments [Member] | Alumina Refining [Member] | Structures [Member]
Property, Plant and Equipment [Line Items]
Properties, plants, and equipment, gross	2,400	2,474
Operating Segments [Member] | Alumina Refining [Member] | Machinery and Equipment [Member]
Property, Plant and Equipment [Line Items]
Properties, plants, and equipment, gross	3,946	4,180
Operating Segments [Member] | Aluminum Smelting and Casting [Member] | Structures [Member]
Property, Plant and Equipment [Line Items]
Properties, plants, and equipment, gross	3,298	3,447
Operating Segments [Member] | Aluminum Smelting and Casting [Member] | Machinery and Equipment [Member]
Property, Plant and Equipment [Line Items]
Properties, plants, and equipment, gross	5,877	6,111
Operating Segments [Member] | Energy [Member] | Structures [Member]
Property, Plant and Equipment [Line Items]
Properties, plants, and equipment, gross	339	360
Operating Segments [Member] | Energy [Member] | Machinery and Equipment [Member]
Property, Plant and Equipment [Line Items]
Properties, plants, and equipment, gross	836	844
Other [Member]
Property, Plant and Equipment [Line Items]
Properties, plants, and equipment, net	374	453
Other [Member] | Structures [Member]
Property, Plant and Equipment [Line Items]
Properties, plants, and equipment, gross	340	350
Other [Member] | Machinery and Equipment [Member]
Property, Plant and Equipment [Line Items]
Properties, plants, and equipment, gross	$ 452	$ 465