Segment Information - Schedule of Segment Adjusted EBITDA to Consolidated Net Income (Loss) Attributable to Alcoa Corporation (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
Segment Reporting Information [Line Items]
Total Segment Adjusted EBITDA	$ 798	$ 189
Transformation	(12)	(14)
Intersegment eliminations	103	(8)
Corporate expenses	(37)	(34)
Provision for depreciation, depletion, and amortization	(148)	(161)
Restructuring and other charges, net (D)	(5)	(202)
Interest expense	(53)	(27)
Other income (expenses), net (P)	26	(59)
Other	(4)	(9)
Consolidated income (loss) before income taxes	668	(325)
(Provision for) benefit from income taxes	(120)	18
Net loss attributable to noncontrolling interest	0	55
NET INCOME (LOSS) ATTRIBUTABLE TO ALCOA CORPORATION	$ 548	$ (252)