Restructuring and Other Charges, Net - Schedule of Restructuring and Other Charges, Net by Reportable Segments, Pretax (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Restructuring Cost And Reserve [Line Items]
Restructuring and other charges, net	$ (75)	$ 33	$ 50	$ 40
Operating Segments [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring and other charges, net	(78)	3	48	18
Corporate [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring and other charges, net	3	30	2	22
Bauxite [Member] | Operating Segments [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring and other charges, net			58
Alumina [Member] | Operating Segments [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring and other charges, net	(83)		(83)
Aluminum Segment [Member] | Operating Segments [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring and other charges, net	$ 5	$ 3	$ 73	$ 18