v3.26.1
Segment Information - Schedule of Segment Adjusted EBITDA to Consolidated Net Income (Loss) Attributable to Alcoa Corporation (Detail) - USD ($)
$ in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Segment Reporting Information [Line Items]        
Total Segment Adjusted EBITDA $ 977 $ 236 $ 1,631 $ 1,034
Transformation (23) (21) (50) (33)
Intersegment eliminations 2 135 9 238
Corporate expenses (60) (45) (99) (82)
Provision for depreciation, depletion, and amortization (173) (153) (335) (301)
Restructuring and other charges, net (D) 4 (14) (14) (19)
Interest expense (36) (56) (71) (109)
Other (expenses) income, net (O) (200) 112 (74) 138
Other (9) (33) (16) (37)
Income before income taxes 482 161 981 829
Provision for income taxes (73) (10) (155) (130)
Net (income) loss attributable to noncontrolling interest (2) 13 6 13
Consolidated net income attributable to Alcoa Corporation $ 407 $ 164 $ 832 $ 712