Restructuring and Other Charges, Net - Schedule of Restructuring and Other Charges, Net by Reportable Segments, Pretax (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges, net	$ 22	$ 652	$ 195	$ 702
Operating Segments
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges, net	3	(3)	170	45
Corporate [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges, net	19	655	25	657
Alumina [Member] | Operating Segments
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges, net	6	$ (3)	8	(28)
Aluminum Segment [Member] | Operating Segments
Restructuring Cost and Reserve [Line Items]
Restructuring and other charges, net	$ (3)		$ 162	$ 73