Fair Value of Derivative Instruments Not Designated as Hedging Instruments (Detail) (Nondesignated, USD $) In Thousands, unless otherwise specified	Jun. 30, 2013	Dec. 31, 2012
Commodity derivative contracts \| Accounts Payable
Derivatives, Fair Value [Line Items]
Liability Derivatives	$ (4,552)	$ (102)
Commodity derivative contracts \| Accounts Receivable
Derivatives, Fair Value [Line Items]
Asset Derivatives	6,088	3,043
Foreign exchange derivative contract \| Accounts Payable
Derivatives, Fair Value [Line Items]
Liability Derivatives	$ (5,551)	$ (1,031)

Fair value before effects of master netting arrangements, of a financial liability or contract with one or more underlyings, notional amount or payment provision or both, and the contract can be net settled by means outside the contract or delivery of an asset.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 20

-Section 55

-Paragraph 7

-URI http://asc.fasb.org/extlink&oid=28370219&loc=SL20226000-175313

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 210

-SubTopic 20

-Section 50

-Paragraph 3

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=20225523&loc=SL20225862-175312

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 4B

-Subparagraph (a),(c)

-URI http://asc.fasb.org/extlink&oid=7476318&loc=SL5624163-113959

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Period Type:	instant