Statement of Consolidated Comprehensive Income (unaudited) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Net (loss) income (H)	$ (58)	$ 340
Other comprehensive (loss) income, net of tax (F):
Change in unrecognized net actuarial loss and prior service cost/benefit related to pension and other postretirement benefits	42	102
Foreign currency translation adjustments	(20)	(13)
Net change in unrecognized gains/losses on cash flow hedges	(282)	530
Total Other comprehensive (loss) income, net of tax	(260)	619
Comprehensive (loss) income	(468)	847
Comprehensive (loss) income	150	112
Comprehensive (loss) income	(318)	959
Alcoa Corporation [Member]
Net (loss) income (H)	(199)	195
Other comprehensive (loss) income, net of tax (F):
Change in unrecognized net actuarial loss and prior service cost/benefit related to pension and other postretirement benefits	41	101
Foreign currency translation adjustments	(22)	1
Net change in unrecognized gains/losses on cash flow hedges	(288)	550
Total Other comprehensive (loss) income, net of tax	(269)	652
Comprehensive (loss) income	(468)	847
Non-controlling Interest [Member]
Net (loss) income (H)	141	145
Other comprehensive (loss) income, net of tax (F):
Change in unrecognized net actuarial loss and prior service cost/benefit related to pension and other postretirement benefits	1	1
Foreign currency translation adjustments	2	(14)
Net change in unrecognized gains/losses on cash flow hedges	6	(20)
Total Other comprehensive (loss) income, net of tax	9	(33)
Comprehensive (loss) income	$ 150	$ 112