Earnings Per Share - Schedule of Computation of Basic and Diluted EPS Attributable to Alcoa Corporation Common Shareholders (Detail) - USD ($) shares in Millions, $ in Millions	3 Months Ended
Mar. 31, 2023	Mar. 31, 2022
Earnings Per Share [Abstract]
Net (loss) income attributable to Alcoa Corporation	$ (231)	$ 469
Average shares outstanding – basic	178	184
Effect of dilutive securities:
Stock units		4
Average shares outstanding – diluted	178	188

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

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