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Restructuring and Other Charges, Net - Schedule of Restructuring and Other Charges by Reportable Segments, Pretax (Detail) - USD ($) $ in Millions | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jun. 30, 2021 | Jun. 30, 2020 | Jun. 30, 2021 | Jun. 30, 2020
Restructuring Cost and Reserve [Line Items] |  |  |  |
Restructuring and other charges, net (D) | $ 33 | $ 37 | $ 40 | $ 39
Operating Segments [Member] |  |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |  |
Restructuring and other charges, net (D) | 3 | 37 | 18 | 41
Corporate [Member] |  |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |  |
Restructuring and other charges, net (D) | 30 |  | 22 | (2)
Alumina [Member] | Operating Segments [Member] |  |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |  |
Restructuring and other charges, net (D) |  |  |  | 2
Aluminum Segment [Member] | Operating Segments [Member] |  |  |  |
Restructuring Cost and Reserve [Line Items] |  |  |  |
Restructuring and other charges, net (D) | $ 3 | $ 37 | $ 18 | $ 39

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- Definition Amount of expenses associated with exit or disposal activities pursuant to an authorized plan. Includes expenses related to certain asset retirement obligations. + References No definition available. + Details
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- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
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