Segment Information - Schedule of Segment Adjusted EBITDA to Consolidated Net (Loss) Income Attributable to Alcoa Corporation (Detail) - USD ($) $ in Millions	3 Months Ended		12 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023
Segment Reporting Information [Line Items]
Total Segment Adjusted EBITDA	$ 189	$ 287
Transformation	(14)	(8)
Intersegment eliminations	(8)	(8)
Corporate expenses	(34)	(30)
Provision for depreciation, depletion, and amortization	(161)	(153)
Restructuring and other charges, net (D)	(202)	(149)
Interest expense	(27)	(26)
Other expenses, net (P)	(59)	(54)
Consolidated loss before income taxes	(325)	(180)
Benefit from (provision for) income taxes	18	(52)
Net loss attributable to noncontrolling interest	55	1
NET LOSS ATTRIBUTABLE TO ALCOA CORPORATION	(252)	(231)	$ (231)
Other [Member]
Segment Reporting Information [Line Items]
Other	$ (9)	$ (39)