Accumulated Other Comprehensive Loss - Summary of Changes in Accumulated Other Comprehensive (Loss) Income by Component (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Pension and other postretirement benefits (O)
Total Other comprehensive income (loss)	$ (952)	$ (1,708)	$ 265
Foreign currency translation
Other comprehensive loss	(174)	(322)	(235)
Cash flow hedges (P)
Net change from periodic revaluations	(119)	(782)
Net amount reclassified to earnings	316	295
Total Accumulated other comprehensive loss	(3,539)	(4,592)
Alcoa Corporation [Member]
Pension and other postretirement benefits (O)
Balance at beginning of period	(882)	(2,536)	(2,282)
Unrecognized net actuarial gain (loss) and prior service cost/benefit	263	550	(545)
Tax (expense) benefit	(42)	(37)	31
Total Other comprehensive income (loss) before reclassifications, net of tax	221	513	(514)
Amortization of net actuarial loss and prior service cost/benefit	723	1,144	269
Tax expense		(3)	(9)
Total amount reclassified from Accumulated other comprehensive loss, net of tax	723	1,141	260
Total Other comprehensive income (loss)	944	1,654	(254)
Balance at end of period	62	(882)	(2,536)
Foreign currency translation
Balance at beginning of period	(2,614)	(2,385)	(2,160)
Other comprehensive loss	(71)	(229)	(225)
Balance at end of period	(2,685)	(2,614)	(2,385)
Cash flow hedges (P)
Balance at beginning of period	(1,096)	(708)	(532)
Net change from periodic revaluations	(119)	(782)	(345)
Tax (expense) benefit	43	140	74
Total Other comprehensive (loss) income before reclassifications, net of tax	(76)	(642)	(271)
Net amount reclassified to earnings	316	295	106
Tax expense	(60)	(41)	(11)
Total amount reclassified from Accumulated other comprehensive loss, net of tax	256	254	95
Total Other comprehensive income (loss)	180	(388)	(176)
Balance at end of period	(916)	(1,096)	(708)
Total Accumulated other comprehensive loss	(3,539)	(4,592)	(5,629)
Alcoa Corporation [Member] | Aluminum Contracts [Member]
Cash flow hedges (P)
Net amount reclassified to earnings	316	288	66
Alcoa Corporation [Member] | Financial Contracts [Member]
Cash flow hedges (P)
Net amount reclassified to earnings		2	15
Alcoa Corporation [Member] | Foreign Exchange Contract [Member]
Cash flow hedges (P)
Net amount reclassified to earnings	(5)	(3)	20
Alcoa Corporation [Member] | Interest Rate Contracts [Member]
Cash flow hedges (P)
Net amount reclassified to earnings	5	8	5
Non-controlling Interest [Member]
Pension and other postretirement benefits (O)
Balance at beginning of period	(13)	(67)	(56)
Unrecognized net actuarial gain (loss) and prior service cost/benefit	7	30	(19)
Tax (expense) benefit		(6)	3
Total Other comprehensive income (loss) before reclassifications, net of tax	7	24	(16)
Amortization of net actuarial loss and prior service cost/benefit	1	30	6
Tax expense			(1)
Total amount reclassified from Accumulated other comprehensive loss, net of tax	1	30	5
Total Other comprehensive income (loss)	8	54	(11)
Balance at end of period	(5)	(13)	(67)
Foreign currency translation
Balance at beginning of period	(937)	(844)	(834)
Other comprehensive loss	(103)	(93)	(10)
Balance at end of period	(1,040)	(937)	(844)
Cash flow hedges (P)
Balance at beginning of period	(1)	(1)	20
Net change from periodic revaluations	2	(2)	(36)
Tax (expense) benefit		1	10
Total Other comprehensive (loss) income before reclassifications, net of tax	2	(1)	(26)
Net amount reclassified to earnings		2	6
Tax expense		(1)	(1)
Total amount reclassified from Accumulated other comprehensive loss, net of tax		1	5
Total Other comprehensive income (loss)	2		(21)
Balance at end of period	1	(1)	(1)
Total Accumulated other comprehensive loss	$ (1,044)	(951)	(912)
Non-controlling Interest [Member] | Financial Contracts [Member]
Cash flow hedges (P)
Net amount reclassified to earnings		1	$ 6
Non-controlling Interest [Member] | Interest Rate Contracts [Member]
Cash flow hedges (P)
Net amount reclassified to earnings		$ 1