Statement of Consolidated Comprehensive Income (unaudited) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
Statement of Comprehensive Income [Abstract]
NET INCOME (LOSS) ATTRIBUTABLE TO ALCOA CORPORATION	$ 548	$ (252)
Net income (loss), Noncontrolling interest	0	(55)
Net income (loss)	548	(307)
Change in unrecognized net actuarial gain/loss and prior service cost/benefit related to pension and other postretirement benefits, Alcoa Corporation	5	9
Change in unrecognized net actuarial gain/loss and prior service cost/benefit related to pension and other postretirement benefits, Noncontrolling interest	0	1
Change in unrecognized net actuarial gain/loss and prior service cost/benefit related to pension and other postretirement benefits	5	10
Foreign currency translation adjustments, Alcoa Corporation	185	(122)
Foreign currency translation adjustments, Noncontrolling interest	0	(54)
Foreign currency translation adjustments	185	(176)
Net change in unrecognized gains/losses on cash flow hedges, Alcoa Corporation	16	130
Net change in unrecognized gains/losses on cash flow hedges, Noncontrolling interest	0	0
Net change in unrecognized gains/losses on cash flow hedges	16	130
Total Other comprehensive income (loss), net of tax, Alcoa Corporation	206	17
Total Other comprehensive income (loss), net of tax, Noncontrolling interest	0	(53)
Total Other comprehensive income (loss), net of tax	206	(36)
Comprehensive income (loss), Alcoa Corporation	754	(235)
Comprehensive income (loss), Noncontrolling interest	0	(108)
Comprehensive income (loss)	$ 754	$ (343)