Segment and Related Information - Additional Information (Detail)	12 Months Ended
	Dec. 31, 2024 Segment Product_Division
Segment Reporting Information [Line Items]
Number of operating segments	2
Number of reportable segments	2
Segment Reporting, CODM, Individual Title and Position or Group Name [Extensible Enumeration]	srt:ChiefExecutiveOfficerMember, srt:PresidentMember
Segment Reporting, CODM, Profit (Loss) Measure, How Used, Description	The Company calculates Segment Adjusted EBITDA as Total sales (third-party and intersegment) minus the following items: Cost of goods sold; Selling, general administrative, and other expenses; and Research and development expenses. Alcoa Corporation’s Segment Adjusted EBITDA may not be comparable to similarly titled measures of other companies. The CODM regularly reviews Segment Adjusted EBITDA to assess performance and allocate resources (including employees, property, and financial or capital resources) in the planning and strategic review process.
Number of product divisions | Product_Division	4
Alcoa Corporation [Member]
Segment Reporting Information [Line Items]
Ownership interest in joint venture	25.10%
AWAC [Member]
Segment Reporting Information [Line Items]
Ownership interest in joint venture	25.10%