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Derivatives and Other Financial Instruments - Schedule of Reconciliation of Activity for Derivative Contracts (Detail) (USD $) In Millions, unless otherwise specified | 3 Months Ended | 6 Months Ended
--- | --- | ---
Jun. 30, 2013 | Jun. 30, 2013
Aluminum Contracts [Member] | Assets [Member] |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |  |
Beginning balance | $ 522 | $ 547
Sales | (1) | (3)
Cost of goods sold | (50) | (102)
Other income (expenses), net | (1) | 16
Other comprehensive loss | 9 | 16
Purchases, sales, issuances, and settlements |  |
Transfers into and (or) out of Level 3 |  |
Foreign currency translation | (47) | (42)
Ending balance | 432 | 432
Sales |  |
Cost of goods sold |  |
Other income (expenses), net | (1) | 16
Aluminum Contracts [Member] | Liabilities [Member] |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |  |
Beginning balance | 478 | 608
Sales | (6) | (14)
Other comprehensive loss | (77) | (199)
Purchases, sales, issuances, and settlements |  |
Transfers into and (or) out of Level 3 |  |
Ending balance | 395 | 395
Sales |  |
Cost of goods sold |  |
Energy Contracts [Member] | Assets [Member] |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |  |
Beginning balance | 8 | 3
Other comprehensive loss | (8) | (3)
Purchases, sales, issuances, and settlements |  |
Transfers into and (or) out of Level 3 |  |
Sales |  |
Cost of goods sold |  |
Embedded Credit Derivative [Member] | Liabilities [Member] |  |
Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items] |  |
Beginning balance | 32 | 30
Other income (expenses), net | 7 | 9
Purchases, sales, issuances, and settlements |  |
Transfers into and (or) out of Level 3 |  |
Ending balance | 39 | 39
Sales |  |
Cost of goods sold |  |
Other income (expenses), net | $ 7 | $ 9

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- Definition Amount of gain (loss) recognized in other comprehensive income (loss) for 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)(1a) -URI http://asc.fasb.org/extlink&oid=25499696&loc=d3e19207-110258 + Details
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