Summary of Significant Accounting Policies - Additional Information (Detail) $ in Millions	12 Months Ended
	Dec. 31, 2021 USD ($) Reporting_Unit Segment	Dec. 31, 2020 USD ($)	Jan. 01, 2020
Summary Of Significant Accounting Policies [Line Items]
Original maturity of cash equivalents	3 months
Segment Allocation, Goodwill Recognized | $	$ 144	$ 145
Number of operating segments | Segment	3
Maximum hedging contracts period, in years	5 years
Accounting Standards Update 2019-12 [Member]
Summary Of Significant Accounting Policies [Line Items]
Change in accounting principle, accounting standards update, adopted			true
Change in accounting principle, accounting standards update, adoption date			Jan. 01, 2021
Change in accounting principle, accounting standards update, immaterial effect			true
Alcoa Corporation [Member]
Summary Of Significant Accounting Policies [Line Items]
Number of reporting units for goodwill allocation	4
Alcoa Corporation [Member] | Bauxite [Member]
Summary Of Significant Accounting Policies [Line Items]
Number of reporting units for goodwill allocation	1
Alcoa Corporation [Member] | Alumina [Member]
Summary Of Significant Accounting Policies [Line Items]
Number of reporting units for goodwill allocation	1
Alcoa Corporation [Member] | Aluminum [Member]
Summary Of Significant Accounting Policies [Line Items]
Number of reporting units for goodwill allocation	2
Minimum [Member] | Bauxite Mining [Member]
Summary Of Significant Accounting Policies [Line Items]
Period of mining	1 year
Maximum [Member] | Bauxite Mining [Member]
Summary Of Significant Accounting Policies [Line Items]
Period of mining	5 years