Statement of Consolidated Comprehensive Income (unaudited) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Statement of Comprehensive Income [Abstract]
NET INCOME ATTRIBUTABLE TO ALCOA CORPORATION	$ 175	$ 80
Net income, Noncontrolling interest	44	59
Net income	219	139
Change in unrecognized net actuarial loss and prior service cost/benefit related to pension and other postretirement benefits, Alcoa Corporation	131	38
Change in unrecognized net actuarial loss and prior service cost/benefit related to pension and other postretirement benefits, Noncontrolling interest	1
Change in unrecognized net actuarial loss and prior service cost/benefit related to pension and other postretirement benefits	132	38
Foreign currency translation adjustments, Alcoa Corporation	(176)	(663)
Foreign currency translation adjustments, Noncontrolling interest	(60)	(245)
Foreign currency translation adjustments	(236)	(908)
Net change in unrecognized gains/losses on cash flow hedges, Alcoa Corporation	(204)	701
Net change in unrecognized gains/losses on cash flow hedges, Noncontrolling interest	(3)	(20)
Net change in unrecognized gains/losses on cash flow hedges	(207)	681
Total Other comprehensive (loss) income, net of tax, Alcoa Corporation	(249)	76
Total Other comprehensive (loss) income, net of tax, Noncontrolling interest	(62)	(265)
Total Other comprehensive (loss) income, net of tax	(311)	(189)
Comprehensive (loss) income, Alcoa Corporation	(74)	156
Comprehensive (loss) income, Noncontrolling interest	(18)	(206)
Comprehensive (loss) income	$ (92)	$ (50)