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, 2021	Dec. 31, 2020	Dec. 31, 2019
Segment Reporting Information [Line Items]
Total Segment Adjusted EBITDA	$ 3,053	$ 1,317	$ 1,626
Transformation	(44)	(45)	(7)
Intersegment eliminations	(101)	(8)	150
Corporate expenses	(129)	(102)	(101)
Provision for depreciation, depletion, and amortization	(664)	(653)	(713)
Restructuring and other charges, net (D)	(1,128)	(104)	(1,031)
Interest expense (U)	(195)	(146)	(121)
Other income (expenses), net (U)	445	(8)	(162)
Income (loss) before income taxes	1,199	173	(438)
Provision for income taxes (Q)	(629)	(187)	(415)
Net income attributable to noncontrolling interest	(141)	(156)	(272)
Net income (loss) attributable to Alcoa Corporation	429	(170)	(1,125)
Other [Member]
Segment Reporting Information [Line Items]
Restructuring and other charges, net (D)	(1,128)	(104)	(1,031)
Other	$ (38)	$ (78)	$ (79)