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Contingencies and Commitments - Additional Information (Detail) In Millions, unless otherwise specified | 1 Months Ended | 3 Months Ended |  |  | 1 Months Ended |  |  | 0 Months Ended |
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Jul. 31, 2012 Plant | Jun. 30, 2012 USD ($) Installment | Jun. 30, 2012 EUR (€) | Mar. 31, 2014 | Mar. 26, 2012 USD ($) | Mar. 26, 2012 EUR (€) | Jun. 30, 2010 t | Nov. 30, 2006 Curtis v. Alcoa Inc. [Member] Person | Feb. 21, 2013 Minimum [Member] USD ($) | Feb. 21, 2013 Maximum [Member] USD ($) | Feb. 21, 2013 Maximum [Member] EUR (€) | Feb. 21, 2013 Alcoa Trasformazioni [Member] USD ($) | Feb. 21, 2013 Alcoa Trasformazioni [Member] EUR (€) | Mar. 31, 2014 Alcoa [Member] USD ($) | Mar. 31, 2014 Alcoa [Member] EUR (€) | Nov. 19, 2009 Italian Government [Member] USD ($) Plant | Nov. 19, 2009 Italian Government [Member] EUR (€) Plant | Jul. 31, 2006 Italian Government [Member] | Dec. 31, 2012 Portovesme [Member] t
Loss Contingencies [Line Items] |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Retired former employees involved in class action |  |  |  |  |  |  |  | 13,000 |  |  |  |  |  |  |  |  |  |  |
Trial length, number of days |  |  |  | 8 days |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Management estimate for maximum exposure from class action |  |  |  |  | $ 110 | € 85 |  |  |  |  |  | $ 97 | € 76 |  |  |  |  |  |
Provision for contract losses |  |  |  |  |  |  |  |  | 0 | 97 | 76 |  |  |  |  |  |  |  |
Number of years operating under a power supply structure |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 10 years |
Charge related to European Commission announcement |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 250 | 173 |  |
Number of smelters | 2 |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 2 | 2 |  |
Write-off of receivable |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 20 | 14 |  |
Establishment reserve |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 230 | 159 |  |
Recovery amount |  | 375 | 303 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Reduction in recovery amount |  | 65 | 53 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Payments to Italian Government |  | 310 | 250 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Payments to Italian Government, installments amount |  | 69 | 50 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Number of installments, litigation payment |  | 5 | 5 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Litigation reserve |  | 218 | 159 |  |  |  |  |  |  |  |  |  |  | 0 |  |  |  |  |
Range of reasonable possible loss, minimum |  | 218 | 159 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Range of reasonable possible loss, maximum |  | 417 | 303 |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |
Noncurrent asset |  |  |  |  |  |  |  |  |  |  |  |  |  | $ 126 | € 91 |  |  |  |
Amount of curtailment, metric-tons-per-year |  |  |  |  |  |  | 44,000 |  |  |  |  |  |  |  |  |  |  |  | 150,000

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