Accumulated Other Comprehensive Loss - Summary of Changes in Accumulated Other Comprehensive (Loss) Income by Component (Parenthetical) (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Accumulated Other Comprehensive Income (Loss) [Line Items]
Settlements and/or curtailments related to retirement benefits	$ (1)	$ 21	$ 632
Net amount reclassified to earnings	288	130
Cost of Goods Sold [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net amount reclassified to earnings	1	5	5
Sales [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net amount reclassified to earnings	(2)	(31)	(10)
Alcoa Corporation [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Settlements and/or curtailments related to retirement benefits	(1)	21	633
Net amount reclassified to earnings	$ 288	130	$ 316
Non-controlling Interest [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Net amount reclassified to earnings		$ (1)