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, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges, net	$ 24	$ (75)	$ 173	$ 50
Operating Segments
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges, net	20	(78)	167	48
Corporate [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges, net	4	3	6	2
Alumina [Member] | Operating Segments
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges, net	1	(83)	2	(25)
Aluminum Segment [Member] | Operating Segments
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges, net	$ 19	$ 5	$ 165	$ 73