Segment Information - Schedule of Segment Adjusted EBITDA to Consolidated Net Income Attributable to Alcoa Corporation (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Segment Reporting Information [Line Items]
Total Segment Adjusted EBITDA	$ 944	$ 625	$ 1,957	$ 1,194
Transformation	(11)	(13)	(25)	(24)
Intersegment eliminations	20	35	122	28
Corporate expenses	(35)	(28)	(64)	(54)
Provision for depreciation, depletion, and amortization	(161)	(161)	(321)	(343)
Restructuring and other charges, net (D)	75	(33)	(50)	(40)
Interest expense	(30)	(67)	(55)	(109)
Other income, net (Q)	206	105	220	129
Income before income taxes	908	461	1,671	773
Provision for income taxes	(234)	(111)	(444)	(204)
Net income attributable to noncontrolling interest	(125)	(41)	(209)	(85)
NET INCOME ATTRIBUTABLE TO ALCOA CORPORATION	549	309	1,018	484
Other [Member]
Segment Reporting Information [Line Items]
Restructuring and other charges, net (D)	75	(33)	(50)	(40)
Other	$ (100)	$ (2)	$ (113)	$ (8)