Statement of Consolidated Comprehensive Income (Loss) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Net income (loss)	$ 871	$ 559	$ (346)
Other comprehensive income (loss) income, net of tax (G):
Change in unrecognized net actuarial loss and prior service cost/benefit related to pension and other postretirement benefits	504	(447)	(202)
Foreign currency translation adjustments	(833)	284	315
Net change in unrecognized gains/losses on cash flow hedges	698	(1,089)	(342)
Total Other comprehensive income (loss), net of tax	369	(1,252)	(229)
Comprehensive income (loss)	1,240	(693)	(575)
Alcoa Corporation [Member]
Net income (loss)	227	217	(400)
Other comprehensive income (loss) income, net of tax (G):
Change in unrecognized net actuarial loss and prior service cost/benefit related to pension and other postretirement benefits	503	(456)	(202)
Foreign currency translation adjustments	(604)	188	213
Net change in unrecognized gains/losses on cash flow hedges	718	(1,139)	(346)
Total Other comprehensive income (loss), net of tax	617	(1,407)	(335)
Comprehensive income (loss)	844	(1,190)	(735)
Non-controlling Interest [Member]
Net income (loss)	644	342	54
Other comprehensive income (loss) income, net of tax (G):
Change in unrecognized net actuarial loss and prior service cost/benefit related to pension and other postretirement benefits	1	9
Foreign currency translation adjustments	(229)	96	102
Net change in unrecognized gains/losses on cash flow hedges	(20)	50	4
Total Other comprehensive income (loss), net of tax	(248)	155	106
Comprehensive income (loss)	$ 396	$ 497	$ 160