Statement of Consolidated Comprehensive Income (unaudited) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Statement of Comprehensive Income [Abstract]
NET INCOME (LOSS) ATTRIBUTABLE TO ALCOA CORPORATION	$ 164	$ 20	$ 712	$ (232)
Net income (loss), Noncontrolling interest	(13)	11	(13)	(44)
Net income (loss)	151	31	699	(276)
Change in unrecognized net actuarial gain/loss and prior service cost/benefit related to pension and other postretirement benefits, Alcoa Corporation	11	13	16	22
Change in unrecognized net actuarial gain/loss and prior service cost/benefit related to pension and other postretirement benefits, Noncontrolling interest	0	5	0	6
Change in unrecognized net actuarial gain/loss and prior service cost/benefit related to pension and other postretirement benefits	11	18	16	28
Foreign currency translation adjustments, Alcoa Corporation	207	(60)	392	(182)
Foreign currency translation adjustments, Noncontrolling interest	10	(16)	10	(70)
Foreign currency translation adjustments	217	(76)	402	(252)
Net change in unrecognized gains/losses on cash flow hedges, Alcoa Corporation	(47)	(62)	(31)	68
Net change in unrecognized gains/losses on cash flow hedges, Noncontrolling interest	(0)	(1)	0	(1)
Net change in unrecognized gains/losses on cash flow hedges	(47)	(63)	(31)	67
Total Other comprehensive income (loss), net of tax, Alcoa Corporation	171	(109)	377	(92)
Total Other comprehensive income (loss), net of tax, Noncontrolling interest	10	(12)	10	(65)
Total Other comprehensive income (loss), net of tax	181	(121)	387	(157)
Comprehensive income (loss), Alcoa Corporation	335	(89)	1,089	(324)
Comprehensive income (loss), Noncontrolling interest	(3)	(1)	(3)	(109)
Comprehensive income (loss)	$ 332	$ (90)	$ 1,086	$ (433)