Accumulated Other Comprehensive Loss - Summary of Changes in Accumulated Other Comprehensive (Loss) Income by Component (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Pension and other postretirement benefits (O)
Total Other comprehensive income (loss)	$ 72	$ (952)	$ (1,708)
Foreign currency translation
Other comprehensive income (loss)	149	(174)	(322)
Cash flow hedges (P)
Net change from periodic revaluations	(295)	(119)
Net amount reclassified to earnings	130	316
Total Accumulated other comprehensive loss	(3,645)	(3,539)
Alcoa Corporation [Member]
Pension and other postretirement benefits (O)
Balance at beginning of period	62	(882)	(2,536)
Unrecognized net actuarial gain (loss) and prior service cost/benefit	(112)	263	550
Tax (expense) benefit	17	(42)	(37)
Total Other comprehensive income (loss) before reclassifications, net of tax	(95)	221	513
Amortization of net actuarial loss and prior service cost/benefit	39	723	1,144
Tax expense	(6)		(3)
Total amount reclassified from Accumulated other comprehensive loss, net of tax	33	723	1,141
Total Other comprehensive income (loss)	(62)	944	1,654
Balance at end of period		62	(882)
Foreign currency translation
Balance at beginning of period	(2,685)	(2,614)	(2,385)
Other comprehensive income (loss)	92	(71)	(229)
Balance at end of period	(2,593)	(2,685)	(2,614)
Cash flow hedges (P)
Balance at beginning of period	(916)	(1,096)	(708)
Net change from periodic revaluations	(295)	(119)	(782)
Tax benefit	70	43	140
Total Other comprehensive (loss) income before reclassifications, net of tax	(225)	(76)	(642)
Net amount reclassified to earnings	130	316	295
Tax expense	(41)	(60)	(41)
Total amount reclassified from Accumulated other comprehensive loss, net of tax	89	256	254
Total Other comprehensive (loss) income	(136)	180	(388)
Balance at end of period	(1,052)	(916)	(1,096)
Total Accumulated other comprehensive loss	(3,645)	(3,539)	(4,592)
Alcoa Corporation [Member] | Aluminum Contracts [Member]
Cash flow hedges (P)
Net amount reclassified to earnings	181	316	288
Alcoa Corporation [Member] | Financial Contracts [Member]
Cash flow hedges (P)
Net amount reclassified to earnings	(20)		2
Alcoa Corporation [Member] | Interest Rate Contracts [Member]
Cash flow hedges (P)
Net amount reclassified to earnings	(5)	5	8
Alcoa Corporation [Member] | Foreign Exchange Contract [Member]
Cash flow hedges (P)
Net amount reclassified to earnings	(26)	(5)	(3)
Non-controlling Interest [Member]
Pension and other postretirement benefits (O)
Balance at beginning of period	(5)	(13)	(67)
Unrecognized net actuarial gain (loss) and prior service cost/benefit	(13)	7	30
Tax (expense) benefit	2		(6)
Total Other comprehensive income (loss) before reclassifications, net of tax	(11)	7	24
Amortization of net actuarial loss and prior service cost/benefit	1	1	30
Total amount reclassified from Accumulated other comprehensive loss, net of tax	1	1	30
Total Other comprehensive income (loss)	(10)	8	54
Balance at end of period	(15)	(5)	(13)
Foreign currency translation
Balance at beginning of period	(1,040)	(937)	(844)
Other comprehensive income (loss)	57	(103)	(93)
Balance at end of period	(983)	(1,040)	(937)
Cash flow hedges (P)
Balance at beginning of period	1	(1)	(1)
Net change from periodic revaluations		2	(2)
Tax benefit			1
Total Other comprehensive (loss) income before reclassifications, net of tax		2	(1)
Net amount reclassified to earnings	(1)		2
Tax expense			(1)
Total amount reclassified from Accumulated other comprehensive loss, net of tax	(1)		1
Total Other comprehensive (loss) income	(1)	2
Balance at end of period		1	(1)
Total Accumulated other comprehensive loss	(998)	$ (1,044)	(951)
Non-controlling Interest [Member] | Financial Contracts [Member]
Cash flow hedges (P)
Net amount reclassified to earnings			1
Non-controlling Interest [Member] | Interest Rate Contracts [Member]
Cash flow hedges (P)
Net amount reclassified to earnings	$ (1)		$ 1