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Long-Term Debt - Additional Information (Detail) $ in Millions | 9 Months Ended
--- | ---
Sep. 30, 2016 USD ($) | Sep. 30, 2015 USD ($)
Debt Instrument [Line Items] |  |
Cash held in escrow | $ 72 | $ 7
Proceeds from issuance of public debt offering | $ 1,313 | $ 1,534
Ratio of consolidated indebtedness to consolidated EBITDDA | 5.50 |
Alcoa Nederland Holding BV [Member] |  |
Debt Instrument [Line Items] |  |
Cash held in escrow | $ 1,309 |
Proceeds from issuance of public debt offering | 1,228 |
Cash on hand to fund redemption of senior notes | $ 81 |
Amended Credit Facility [Member] |  |
Debt Instrument [Line Items] |  |
Revolving credit facility, term | 5 years |
Ratio of Indebtedness December 31, 2019 and Thereafter [Member] |  |
Debt Instrument [Line Items] |  |
Declining ratio of consolidated indebtedness to consolidated EBITDDA | 3.50 |
Line of Credit Prior to Amendment [Member] |  |
Debt Instrument [Line Items] |  |
Replacement of existing financial covenant | $ 4,000 |
Post Amendment [Member] |  |
Debt Instrument [Line Items] |  |
Replacement of existing financial covenant | 3,000 |
6.75% Senior Notes Due 2024 [Member] | Alcoa Nederland Holding BV [Member] |  |
Debt Instrument [Line Items] |  |
Principal amount of debt | $ 750 |
Senior notes, interest percentage | 6.75% |
Debt instrument maturity date | 2024 |
7% Senior Notes Due 2026 [Member] | Alcoa Nederland Holding BV [Member] |  |
Debt Instrument [Line Items] |  |
Principal amount of debt | $ 500 |
Senior notes, interest percentage | 7.00% |
Debt instrument maturity date | 2026 |

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