Segment Information - Schedule of Segment Adjusted EBITDA to Consolidated Net Income Attributable to Alcoa Corporation (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Segment Reporting Information [Line Items]
Total Segment Adjusted EBITDA	$ 1,013	$ 569
Transformation	(14)	(11)
Intersegment eliminations	102	(7)
Corporate expenses	(29)	(26)
Provision for depreciation, depletion, and amortization	(160)	(182)
Restructuring and other charges, net (D)	(125)	(7)
Interest expense	(25)	(42)
Other income, net (P)	14	24
Income before income taxes	763	312
Provision for income taxes	(210)	(93)
Net income attributable to noncontrolling interest	(84)	(44)
NET INCOME ATTRIBUTABLE TO ALCOA CORPORATION	469	175
Other [Member]
Segment Reporting Information [Line Items]
Restructuring and other charges, net (D)	(125)	(7)
Other	$ (13)	$ (6)