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Earnings Per Share (Tables) | 6 Months Ended
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Jun. 30, 2021
Earnings Per Share [Abstract] |
Schedule of Computation of Basic and Diluted EPS Attributable to Alcoa Corporation Common Shareholders | The information used to compute basic and diluted EPS attributable to Alcoa Corporation common shareholders was as follows (shares in millions):
|  | Second quarter ended June 30, |  |  | Six months ended June 30, |
|  | 2021 |  |  | 2020 |  |  | 2021 |  |  | 2020 |
Net income (loss) attributable to Alcoa Corporation |  | $ | 309 |  |  | $ | (197 | ) |  | $ | 484 |  |  | $ | (117 | )
Average shares outstanding – basic |  |  | 187 |  |  |  | 186 |  |  |  | 186 |  |  |  | 186 |
Effect of dilutive securities: |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Stock options |  |  | — |  |  |  | — |  |  |  | — |  |  |  | — |
Stock units |  |  | 3 |  |  |  | — |  |  |  | 3 |  |  |  | — |
Average shares outstanding – diluted |  |  | 190 |  |  |  | 186 |  |  |  | 189 |  |  |  | 186 |

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- Definition Tabular disclosure of an entity's basic and diluted earnings per share calculations, including a reconciliation of numerators and denominators of the basic and diluted per-share computations for income from continuing operations. + References Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef -Publisher FASB -Name Accounting Standards Codification -Topic 260 -SubTopic 10 -Section 50 -Paragraph 1 -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=6371337&loc=d3e3550-109257 + Details
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