Segment Information - Schedule of Sales by Product Division (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Disaggregation Of Revenue [Line Items]
Sales	$ 2,670	$ 3,293
Aluminum [Member]
Disaggregation Of Revenue [Line Items]
Sales	1,846	2,447
Alumina [Member]
Disaggregation Of Revenue [Line Items]
Sales	714	850
Energy [Member]
Disaggregation Of Revenue [Line Items]
Sales	28	41
Bauxite [Member]
Disaggregation Of Revenue [Line Items]
Sales	127	28
Other [Member]
Disaggregation Of Revenue [Line Items]
Sales	$ (45)	$ (73)