Statement of Consolidated Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Statement of Comprehensive Income [Abstract]
Net income (loss) attributable to Alcoa Corporation	$ 60	$ (651)	$ (123)
Net income (loss) , Noncontrolling interest	(36)	(122)	161
Net income (loss)	24	(773)	38
Change in unrecognized net actuarial gain/loss and prior service cost/benefit related to pension and other postretirement benefits, Alcoa Corporation	0	(62)	944
Change in unrecognized net actuarial gain/loss and prior service cost/benefit related to pension and other postretirement benefits, Noncontrolling interest	4	(10)	8
Change in unrecognized net actuarial gain/loss and prior service cost/benefit related to pension and other postretirement benefits	4	(72)	952
Foreign currency translation adjustments, Alcoa Corporation	(513)	92	(71)
Foreign currency translation adjustments, Noncontrolling interest	(105)	57	(103)
Foreign currency translation adjustments	(618)	149	(174)
Net change in unrecognized gains/losses on cash flow hedges, Alcoa Corporation	147	(136)	180
Net change in unrecognized gains/losses on cash flow hedges, Noncontrolling interest	0	(1)	2
Net change in unrecognized gains/losses on cash flow hedges	147	(137)	182
Total Other comprehensive (loss) income, net of tax, Alcoa Corporation	(366)	(106)	1,053
Total Other comprehensive (loss) income, net of tax, Noncontrolling interest	(101)	46	(93)
Total Other comprehensive (loss) income, net of tax	(467)	(60)	960
Comprehensive (loss) income, Alcoa Corporation	(306)	(757)	930
Comprehensive (loss) income, Noncontrolling interest	(137)	(76)	68
Comprehensive (loss) income	$ (443)	$ (833)	$ 998