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Derivatives and Other Financial Instruments - Additional Information (Detail) In Millions, unless otherwise specified | 1 Months Ended | 3 Months Ended |  |  |  | 3 Months Ended |  |  | 1 Months Ended
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Jul. 31, 2012 Plant Contract | Mar. 31, 2014 USD ($) t Contract | Mar. 31, 2014 CAD | Dec. 31, 2013 USD ($) | Sep. 30, 2012 USD ($) | Mar. 31, 2014 Forward Contracts [Member] USD ($) | Mar. 31, 2014 Forward Contracts [Member] BRL | Mar. 31, 2014 Level 3 [Member] USD ($) | Dec. 31, 2013 Level 3 [Member] USD ($) | Jul. 31, 2012 Power Contract One [Member] | Jul. 31, 2012 Power Contract Two [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] |  |  |  |  |  |  |  |  |  |  |
Net unrealized loss on derivative contracts |  |  |  |  |  |  |  | $ 67 |  |  |
Other derivative contracts estimated term of quoted market prices, in years |  | 10 years |  |  |  |  |  |  |  |  |
Number of contracts | 2 |  |  |  |  |  |  |  |  |  |
Power contracts maturity date |  |  |  |  |  |  |  |  |  | Mar. 31, 2014 | Mar. 31, 2016
Number of smelters | 2 |  |  |  |  |  |  |  |  |  |
Derivative asset amount |  | 371 |  | 390 | 596 |  |  | 337 | 355 |  |
Power purchase period forecasted by derivative instrument |  | Through December 2036 |  |  |  |  |  |  |  |  |
Period of natural gas supply contract |  | 6 years |  |  |  |  |  |  |  |  |
Number of commodities involved for valuation of supply contract |  | 2 |  |  |  |  |  |  |  |  |
Number of contracts ceased to qualify as fair value hedge |  | 0 |  |  |  |  |  |  |  |  |
Amount of aluminum kmt designated as fair value hedges |  | 347,000 |  |  |  |  |  |  |  |  |
Derivative designated as fair value hedge start period |  | 2014 |  |  |  |  |  |  |  |  |
Derivative designated as fair value hedge end period |  | 2018 |  |  |  |  |  |  |  |  |
Face amount of debt the hedges effectively convert from fixed to floating through 2018 |  | 200 |  |  |  |  |  |  |  |  |
Interest rate cash flow hedges |  | 0 |  |  |  |  |  |  |  |  |
Forward contract to purchase to mitigate the foreign currency risk related to a Canadian/Brazilian-denominated loan due in 2014 |  | 53 | 58 |  |  | 231 | 543 |  |  |  |
Maturity date of forward contract |  |  |  |  |  | Mar. 31, 2014 | Mar. 31, 2014 |  |  |  |
Loss recognized on forward contract |  | $ 4 |  |  |  |  |  |  |  |  |

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- Definition Aluminum futures designated as fair value hedges in kilo metric ton. + References No definition available. + Details
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- Definition Derivative designated as fair value hedge end period. + References No definition available. + Details
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- Definition Interest rate cash flow hedges. + References No definition available. + Details
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- Definition Number of commodities involved for valuation of supply contract. + References No definition available. + Details
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- Definition Number of contracts ceased to qualify as fair value hedge. + References No definition available. + Details
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- Definition Other derivative contracts estimated term of quoted market prices, in years. + References No definition available. + Details
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- Definition Power purchase agreement period forecasted by derivative instrument. + References No definition available. + Details
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- Definition Date the derivative contract matures, in CCYY-MM-DD format. + References No definition available. + Details
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- Details
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- Definition Fair value of financial instrument classified as an asset measured using unobservable inputs that reflect the entity's own assumption about the assumptions market participants would use in pricing. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 820 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=25499696&loc=d3e19207-110258 + Details
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