Accumulated Other Comprehensive Loss - Summary of Changes in Accumulated Other Comprehensive (Loss) Income by Component (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022	Dec. 31, 2022
Pension and other postretirement benefits (M)
Total Other comprehensive income	$ (4)	$ (23)
Foreign currency translation
Other comprehensive income	17	424
Cash flow hedges (N)
Net change from periodic revaluations	(187)	(1,063)
Net amount reclassified to earnings	37	114
Total Accumulated other comprehensive loss	(3,655)		$ (3,539)
Alcoa Corporation [Member]
Pension and other postretirement benefits (M)
Balance at beginning of period	62	(882)
Unrecognized net actuarial loss and prior service cost/benefit		(7)
Tax benefit		1
Total Other comprehensive loss before reclassifications, net of tax		(6)
Amortization of net actuarial loss and prior service cost/benefit	4	28
Total amount reclassified from Accumulated other comprehensive loss, net of tax	4	28
Total Other comprehensive income	4	22
Balance at end of period	66	(860)
Foreign currency translation
Balance at beginning of period	(2,685)	(2,614)
Other comprehensive income	2	326
Balance at end of period	(2,683)	(2,288)
Cash flow hedges (N)
Balance at beginning of period	(916)	(1,096)
Net change from periodic revaluations	(187)	(1,063)
Tax benefit	38	153
Total Other comprehensive (loss) income before reclassifications, net of tax	(149)	(910)
Net amount reclassified to earnings	37	114
Tax expense	(10)	(34)
Total amount reclassified from Accumulated other comprehensive loss, net of tax	27	80
Total Other comprehensive (loss) income	(122)	(830)
Balance at end of period	(1,038)	(1,926)
Total Accumulated other comprehensive loss	(3,655)	(5,074)
Alcoa Corporation [Member] | Aluminum Contracts [Member]
Cash flow hedges (N)
Net amount reclassified to earnings	61	110
Alcoa Corporation [Member] | Financial Contracts [Member]
Cash flow hedges (N)
Net amount reclassified to earnings	(20)
Alcoa Corporation [Member] | Interest Rate Contracts [Member]
Cash flow hedges (N)
Net amount reclassified to earnings	1	4
Alcoa Corporation [Member] | Foreign Exchange Contract [Member]
Cash flow hedges (N)
Net amount reclassified to earnings	(5)
Non-controlling Interest [Member]
Pension and other postretirement benefits (M)
Balance at beginning of period	(5)	(13)
Amortization of net actuarial loss and prior service cost/benefit		1
Total amount reclassified from Accumulated other comprehensive loss, net of tax		1
Total Other comprehensive income		1
Balance at end of period	(5)	(12)
Foreign currency translation
Balance at beginning of period	(1,040)	(937)
Other comprehensive income	15	98
Balance at end of period	(1,025)	(839)
Cash flow hedges (N)
Balance at beginning of period	1	(1)
Net change from periodic revaluations		1
Total Other comprehensive (loss) income before reclassifications, net of tax		1
Total Other comprehensive (loss) income		1
Balance at end of period	1
Total Accumulated other comprehensive loss	$ (1,029)	$ (851)