Contingencies and Commitments - Additional Information - 2 (Detail) € in Millions	12 Months Ended
	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2014 USD ($)	Dec. 31, 2016 EUR (€)
Loss Contingencies [Line Items]
Total combined assessments	$ 258,000,000			€ 246
Operating leases, expense	110,000,000	$ 112,000,000	$ 112,000,000
Long-term operating leases, minimum annual rentals due in 2017	115,000,000
Long-term operating leases, minimum annual rentals due in 2018	96,000,000
Long-term operating leases, minimum annual rentals due in 2019	75,000,000
Long-term operating leases, minimum annual rentals due in 2020	54,000,000
Long-term operating leases, minimum annual rentals due in 2021	38,000,000
Long-term operating leases, minimum annual rentals due thereafter	116,000,000
Guarantees of third party related to project financing	51,000,000
Letters of credit, total amount committed	$ 212,000,000
Letters of credit, expiration date	2017
Total amount committed under outstanding surety bonds	$ 120,000,000
Surety bonds, expiration date	2017
Other Noncurrent Liabilities and Deferred Credits [Member]
Loss Contingencies [Line Items]
Combined fair value of guarantees	$ 35,000,000
Separation Agreement [Member]
Loss Contingencies [Line Items]
Guarantees of third party related to project financing	354,000,000
Total amount committed under outstanding surety bonds	22,000,000
Supply Agreement [Member]
Loss Contingencies [Line Items]
Guarantees of third party related to project financing	1,600,000,000
Purchase Agreement [Member]
Loss Contingencies [Line Items]
Guarantees of third party related to project financing	245,000,000
Alcoa Corporation Energy Supply Contracts Guarantee [Member]
Loss Contingencies [Line Items]
Guarantees of third party related to project financing	50,000,000
Alcoa Corporation Environmental Liabilities Guarantee [Member]
Loss Contingencies [Line Items]
Guarantees of third party related to project financing	53,000,000
Alcoa Corporation Workers Compensation Claims [Member]
Loss Contingencies [Line Items]
Letters of credit, total amount committed	62,000,000
Alcoa Corporation Equipment Leases And Energy Contracts [Member]
Loss Contingencies [Line Items]
Letters of credit, total amount committed	$ 103,000,000
Minimum [Member] | Separation Agreement [Member]
Loss Contingencies [Line Items]
Guarantees, expiration date	2017
Minimum [Member] | Outstanding bank guarantees [Member]
Loss Contingencies [Line Items]
Guarantees, expiration date	2017
Maximum [Member] | Separation Agreement [Member]
Loss Contingencies [Line Items]
Guarantees, expiration date	2024
Maximum [Member] | Outstanding bank guarantees [Member]
Loss Contingencies [Line Items]
Guarantees, expiration date	2026
Energy Raw Materials And Other Goods And Services [Member]
Loss Contingencies [Line Items]
Purchase obligations due in 2017	$ 490,000,000
Purchase obligations due in 2018	90,000,000
Purchase obligations due in 2019	73,000,000
Purchase obligations due in 2020	64,000,000
Purchase obligations due in 2021	2,000,000
Purchase obligations due thereafter	$ 5,000,000