Accumulated Other Comprehensive Loss - Summary of Changes in Accumulated Other Comprehensive (Loss) Income by Component (Detail) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022	Dec. 31, 2022
Pension and other postretirement benefits (M)
Total Other comprehensive income (loss)	$ (8)	$ (52)	$ (12)	$ (75)
Foreign currency translation
Other comprehensive income (loss)	36	(502)	53	(78)
Cash flow hedges (N)
Net change from periodic revaluations	241	1,184	54	121
Net amount reclassified to earnings	27	129	64	243
Total Accumulated other comprehensive loss	(3,394)		(3,394)		$ (3,539)
Alcoa Corporation [Member]
Pension and other postretirement benefits (M)
Balance at beginning of period	66	(860)	62	(882)
Unrecognized net actuarial loss and prior service cost/benefit	(18)	30	(18)	23
Tax benefit (expense)	8	(6)	8	(5)
Total Other comprehensive (loss) income before reclassifications, net of tax	(10)	24	(10)	18
Amortization of net actuarial loss and prior service cost/benefit	26	29	30	57
Tax expense	(6)	(1)	(6)	(1)
Total amount reclassified from Accumulated other comprehensive loss, net of tax	20	28	24	56
Total Other comprehensive income (loss)	10	52	14	74
Balance at end of period	76	(808)	76	(808)
Foreign currency translation
Balance at beginning of period	(2,683)	(2,288)	(2,685)	(2,614)
Other comprehensive income (loss)	25	(370)	27	(44)
Balance at end of period	(2,658)	(2,658)	(2,658)	(2,658)
Cash flow hedges (N)
Balance at beginning of period	(1,038)	(1,926)	(916)	(1,096)
Net change from periodic revaluations	241	1,184	54	121
Tax expense	(38)	(164)		(11)
Total Other comprehensive income before reclassifications, net of tax	203	1,020	54	110
Net amount reclassified to earnings	27	129	64	243
Tax expense	(4)	(12)	(14)	(46)
Total amount reclassified from Accumulated other comprehensive loss, net of tax	23	117	50	197
Total Other comprehensive income	226	1,137	104	307
Balance at end of period	(812)	(789)	(812)	(789)
Total Accumulated other comprehensive loss	(3,394)	(4,255)	(3,394)	(4,255)
Alcoa Corporation [Member] | Aluminum Contracts [Member]
Cash flow hedges (N)
Net amount reclassified to earnings	33	132	94	242
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	(3)		(2)	4
Alcoa Corporation [Member] | Foreign Exchange Contract [Member]
Cash flow hedges (N)
Net amount reclassified to earnings	(3)	(3)	(8)	(3)
Non-controlling Interest [Member]
Pension and other postretirement benefits (M)
Balance at beginning of period	(5)	(12)	(5)	(13)
Unrecognized net actuarial loss and prior service cost/benefit	(2)	1	(2)	1
Total Other comprehensive (loss) income before reclassifications, net of tax	(2)	1	(2)	1
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 (loss)	(2)		(2)	1
Balance at end of period	(7)	(12)	(7)	(12)
Foreign currency translation
Balance at beginning of period	(1,025)	(839)	(1,040)	(937)
Other comprehensive income (loss)	11	(132)	26	(34)
Balance at end of period	(1,014)	(971)	(1,014)	(971)
Cash flow hedges (N)
Balance at beginning of period	1		1	(1)
Net change from periodic revaluations		1		2
Total Other comprehensive income before reclassifications, net of tax		1		2
Total Other comprehensive income		1		2
Balance at end of period	1	1	1	1
Total Accumulated other comprehensive loss	$ (1,020)	$ (982)	$ (1,020)	$ (982)