Segment Information - Schedule of Segment Adjusted EBITDA to Consolidated Net (Loss) Income Attributable to Alcoa Corporation (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Segment Reporting Information [Line Items]
Total Segment Adjusted EBITDA	$ 132	$ 230	$ 562	$ 2,199
Transformation	(29)	(19)	(54)	(44)
Intersegment eliminations	(4)	23	19	133
Corporate expenses	(33)	(27)	(87)	(91)
Provision for depreciation, depletion, and amortization	(163)	(149)	(469)	(470)
Restructuring and other charges, net (D)	(22)	(652)	(195)	(702)
Interest expense	(26)	(25)	(79)	(80)
Other (expenses) income, net (R)	(85)	(35)	(145)	185
Income before income taxes	(228)	(729)	(507)	942
Benefit from (provision for) income taxes	35	(40)	(39)	(484)
Net loss (income) attributable to noncontrolling interest	25	23	45	(186)
NET (LOSS) INCOME ATTRIBUTABLE TO ALCOA CORPORATION	(168)	(746)	(501)	272
Other [Member]
Segment Reporting Information [Line Items]
Other	$ 2	$ (75)	$ (59)	$ (188)