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Derivative Instruments and Fair Value Measurements - Summary of Fair Value of Open Commodity Derivatives (Detail) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014
Unrealized Gain on Commodity Derivatives [Member] | Commodity Derivatives [Member]
Derivatives, Fair Value [Line Items]
Derivatives not designated as hedging instruments, fair value of assets derivative	$ 6,737	$ 39,951

X

- Definition

Fair value as of the balance sheet date of derivative instrument not designated as hedging instrument and classified as an asset.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4B
-Subparagraph (c)(2)
-URI http://asc.fasb.org/extlink&oid=56946850&loc=SL5624163-113959

+ Details

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X

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

+ Details

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- Details

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- Details

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