Derivative Instruments (Details 3) (Not Designated as Hedging Instrument [Member], Commodity Contract [Member], Derivative Liability [Member], USD $) In Thousands, unless otherwise specified	Dec. 31, 2012
Not Designated as Hedging Instrument [Member] \| Commodity Contract [Member] \| Derivative Liability [Member]
Effect of Non-designated Derivative Instruments on the Consolidated Balance Sheet
Commodity Derivatives, fair value	$ (233)

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

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=7476318&loc=SL5624163-113959

Name:	us-gaap_DerivativeInstrumentsNotDesignatedAsHedgingInstrumentsLiabilityAtFairValue
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant