Statement of Consolidated Operations (unaudited) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Income Statement [Abstract]
Sales (E)	$ 2,995	$ 2,904	$ 9,382	$ 8,409
Cost of goods sold (exclusive of expenses below)	2,695	2,393	7,785	7,330
Selling, general administrative, and other expenses	78	66	231	195
Research and development expenses	11	16	35	40
Provision for depreciation, depletion, and amortization	160	159	461	483
Restructuring and other charges, net (D)	885	30	904	250
Interest expense	33	44	142	111
Other (income) expenses, net (Q)	(1,034)	12	(1,172)	49
Total costs and expenses	2,828	2,720	8,386	8,458
Consolidated income (loss) before income taxes	167	184	996	(49)
(Benefit from) provision for income taxes	(51)	86	79	129
Net income (loss)	218	98	917	(178)
Less: Net (loss) income attributable to noncontrolling interest	(14)	8	(27)	(36)
NET INCOME (LOSS) ATTRIBUTABLE TO ALCOA CORPORATION	$ 232	$ 90	$ 944	$ (142)
EARNINGS PER SHARE ATTRIBUTABLE TO ALCOA CORPORATION COMMON SHAREHOLDERS (F):
Basic	$ 0.88	$ 0.39	$ 3.59	$ (0.72)
Diluted	$ 0.88	$ 0.38	$ 3.57	$ (0.72)