Segment and Related Information - Schedule of Segment Adjusted EBITDA to Consolidated Net (Loss) Income Attributable to Alcoa Corporation (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Segment Reporting Information [Line Items]
Total Segment Adjusted EBITDA	$ 2,065	$ 734	$ 2,280
Transformation	(62)	(80)	(66)
Intersegment eliminations	(231)	7	138
Corporate expenses	(160)	(133)	(128)
Provision for depreciation, depletion, and amortization	(642)	(632)	(617)
Restructuring and other charges, net (D)	(341)	(184)	(696)
Interest expense (U)	(156)	(107)	(106)
Other (expenses) income, net (U)	(91)	(134)	118
Income (Loss) before income taxes	289	(584)	702
Provision for income taxes (Q)	(265)	(189)	(664)
Net loss (income) attributable to noncontrolling interest	36	122	(161)
Net income (loss) attributable to Alcoa Corporation	60	(651)	(123)
Other [Member]
Segment Reporting Information [Line Items]
Restructuring and other charges, net (D)	(341)	(184)	(696)
Other	$ (93)	$ (55)	$ (221)