Accumulated Other Comprehensive Loss - Summary of Changes in Accumulated Other Comprehensive (Loss) Income by Component (Detail) - USD ($)	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023
Pension and other postretirement benefits (L)
Total Other comprehensive income (loss)	$ (10,000,000)	$ (4,000,000)
Foreign currency translation
Other comprehensive (loss) income	(176,000,000)	17,000,000
Cash flow hedges (M)
Net change from periodic revaluations	117,000,000	(187,000,000)
Net amount reclassified to earnings	53,000,000	37,000,000
Total Accumulated other comprehensive loss	(3,628,000,000)		$ (3,645,000,000)
Alcoa Corporation [Member]
Pension and other postretirement benefits (L)
Balance at beginning of period		62,000,000
Unrecognized net actuarial gain/loss and prior service cost/benefit	4,000,000
Tax benefit (expense)	(1,000,000)
Total Other comprehensive income (loss) before reclassifications, net of tax	3,000,000
Amortization of net actuarial gain/loss and prior service cost/benefit	6,000,000	4,000,000
Total amount reclassified from Accumulated other comprehensive loss, net of tax	6,000,000	4,000,000
Total Other comprehensive income (loss)	9,000,000	4,000,000
Balance at end of period	9,000,000	66,000,000
Foreign currency translation
Balance at beginning of period	(2,593,000,000)	(2,685,000,000)
Other comprehensive (loss) income	(122,000,000)	2,000,000
Balance at end of period	(2,715,000,000)	(2,683,000,000)
Cash flow hedges (M)
Balance at beginning of period	(1,052,000,000)	(916,000,000)
Net change from periodic revaluations	117,000,000	(187,000,000)
Tax (expense) benefit	(31,000,000)	38,000,000
Total Other comprehensive income (loss) before reclassifications, net of tax	86,000,000	(149,000,000)
Net amount reclassified to earnings	53,000,000	37,000,000
Tax expense	(9,000,000)	(10,000,000)
Total amount reclassified from Accumulated other comprehensive loss, net of tax	44,000,000	27,000,000
Total Other comprehensive income (loss)	130,000,000	(122,000,000)
Balance at end of period	(922,000,000)	(1,038,000,000)
Total Accumulated other comprehensive loss	(3,628,000,000)	(3,655,000,000)
Alcoa Corporation [Member] | Aluminum Contracts [Member]
Cash flow hedges (M)
Net amount reclassified to earnings	57,000,000	61,000,000
Alcoa Corporation [Member] | Financial Contracts [Member]
Cash flow hedges (M)
Net amount reclassified to earnings		(20,000,000)
Alcoa Corporation [Member] | Interest Rate Contracts [Member]
Cash flow hedges (M)
Net amount reclassified to earnings		1,000,000
Alcoa Corporation [Member] | Foreign Exchange Contract [Member]
Cash flow hedges (M)
Net amount reclassified to earnings	(4,000,000)	(5,000,000)
Non-controlling Interest [Member]
Pension and other postretirement benefits (L)
Balance at beginning of period	(15,000,000)	(5,000,000)
Amortization of net actuarial gain/loss and prior service cost/benefit	1,000,000
Total amount reclassified from Accumulated other comprehensive loss, net of tax	1,000,000
Total Other comprehensive income (loss)	1,000,000
Balance at end of period	(14,000,000)	(5,000,000)
Foreign currency translation
Balance at beginning of period	(983,000,000)	(1,040,000,000)
Other comprehensive (loss) income	(54)	15
Balance at end of period	(1,037,000,000)	(1,025,000,000)
Cash flow hedges (M)
Balance at beginning of period		1,000,000
Balance at end of period		1,000,000
Total Accumulated other comprehensive loss	$ (1,051,000,000)	$ (1,029,000,000)