Financial Instruments and Concentrations of Risk (Details 3) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2012	Dec. 31, 2011
Other Current Assets [Member]
Schedule of Not Designated Commodity Derivative Instruments Fair Value on Condensed Consolidated Balance Sheets
Fair value of commodity derivative instruments on assets	$ 0	$ 162
Other Current Liabilities [Member]
Schedule of Not Designated Commodity Derivative Instruments Fair Value on Condensed Consolidated Balance Sheets
Other Derivatives Not Designated as Hedging Instruments Liabilities at Fair Value	$ 1,034	$ 0

Fair value of all derivative liabilities not designated as a hedging instrument.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 825

-SubTopic 10

-Section 50

-Paragraph 10

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=7491637&loc=d3e13433-108611

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 107

-Paragraph 10

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant