Restructuring and Other Charges, Net - Additional Information (Detail)
$ in Millions

1 Months Ended

3 Months Ended

9 Months Ended

12 Months Ended

Sep. 30, 2025

USD ($)

Employees

Sep. 30, 2025

USD ($)

Employees

Dec. 31, 2024

USD ($)

Sep. 30, 2024

USD ($)

Jun. 30, 2024

USD ($)

Mar. 31, 2024

USD ($)

Sep. 30, 2025

USD ($)

Employees

Dec. 31, 2024

USD ($)

Sep. 30, 2024

USD ($)

Dec. 31, 2024

USD ($)

Restructuring Cost and Reserve [Line Items]

Restructuring And Other Charges

$ 885

$ 30

$ 904

$ 250

Cash payment for restructuring

159

$ 183

Restructuring and other charges, net

$ 885

$ 904

250

Kwinana Refinery [Member]

Restructuring Cost and Reserve [Line Items]

Severance costs

$ 41

Number of employees | Employees

220

Asset impairments

Payments related to other costs

$ 46

$ 132

Restructuring and other charges, net

$ 82

$ 8

197

Kwinana Alumina Refinery [Member]

Restructuring Cost and Reserve [Line Items]

Restructuring And Other Charges

205

Asset impairments

$ 265

Accrue for other costs

Remaining cash outlays expected through 2025

Other costs

Cash outlays expected over next six years

600

Charges for write-off remaining net book value of assets.

Reserves for asset retirement obligations and environmental remediation

430

Restructuring and other charges, net

856

Pension Benefits [Member]

Restructuring Cost and Reserve [Line Items]

Settlement of certain other postretirement benefits

^[1]

(1)

Alcoa Corporation [Member]

Restructuring Cost and Reserve [Line Items]

Noncurrent portion of the reserve

$ 30

$ 8

Intalco [Member]

Restructuring Cost and Reserve [Line Items]

Restructuring and other charges, net

2024 Restructuring Plans Action [Member]

Restructuring Cost and Reserve [Line Items]

Restructuring and other charges, net

250

2025 Restructuring Plans Action [Member]

Restructuring Cost and Reserve [Line Items]

Restructuring and other charges, net

885

904

Environmental and Asset Retirement Obligation Reserves [Member]

Restructuring Cost and Reserve [Line Items]

Restructuring and other charges, net

Certain Employee Obligations [Member] | San Ciprian Aluminum Smelter [Member]

Restructuring Cost and Reserve [Line Items]

Restructuring And Other Charges

Severance and Employee Termination Costs [Member]

Restructuring Cost and Reserve [Line Items]

Cash payment for restructuring

Other Exit Costs [Member]

Restructuring Cost and Reserve [Line Items]

Cash payment for restructuring

157

$ 145

Water Management Costs [Member] | Kwinana Refinery [Member]

Restructuring Cost and Reserve [Line Items]

Restructuring And Other Charges

(123)

Other Restructuring [Member] | Kwinana Refinery [Member]

Restructuring Cost and Reserve [Line Items]

Restructuring And Other Charges

136

Asset Retirement Obligations [Member] | Kwinana Refinery [Member]

Restructuring Cost and Reserve [Line Items]

Restructuring And Other Charges

$ (6)

Take Or-Pay Contracts [Member] | Kwinana Refinery [Member]

Restructuring Cost and Reserve [Line Items]

Restructuring And Other Charges

$ (13)

Contract Costs [Member]

Restructuring Cost and Reserve [Line Items]

Restructuring and other charges, net

$ 7

$ 4

$ (3)

$ 16

[1]	These amounts were reported in Restructuring and other charges, net on the accompanying Statement of Consolidated Operations and Cash Flows.

Alcoa Corp 10-Q