Segment Information - Schedule of Segment Adjusted EBITDA to Consolidated Net Income (Loss) Attributable to Alcoa Corporation (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Segment Reporting Information [Line Items]
Total Segment Adjusted EBITDA	$ 547	$ 132	$ 1,155	$ 562
Transformation	(14)	(29)	(44)	(54)
Intersegment eliminations	(38)	(4)	(75)	19
Corporate expenses	(39)	(33)	(114)	(87)
Provision for depreciation, depletion, and amortization	(159)	(163)	(483)	(469)
Restructuring and other charges, net (D)	(30)	(22)	(250)	(195)
Interest expense	(44)	(26)	(111)	(79)
Other expenses, net (P)	(12)	(85)	(49)	(145)
Other	(27)	2	(78)	(59)
Consolidated income (loss) before income taxes	184	(228)	(49)	(507)
(Provision for) benefit from income taxes	(86)	35	(129)	(39)
Net (income) loss attributable to noncontrolling interest	(8)	25	36	45
NET INCOME (LOSS) ATTRIBUTABLE TO ALCOA CORPORATION	$ 90	$ (168)	$ (142)	$ (501)