Derivative Financial Instruments (Schedule Of Revenues And Cost Of Goods Sold) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2010
Revenue [Member]
Trading Activity, Gains and Losses, Net [Line Items]
Net in revenue	$ 26,563	$ 133,619	$ 30,252
Cost Of Goods Sold [Member]
Trading Activity, Gains and Losses, Net [Line Items]
Net in revenue	$ 26,072	$ 132,234	$ 30,283

The net gain (loss) on trading activities (including both derivative and nonderivative instruments) recognized in the statement of financial performance.

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 133

-Paragraph 44C

-Subparagraph c

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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.

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 133

-Paragraph 205H

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 815

-SubTopic 10

-Section 50

-Paragraph 4F

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=7476318&loc=SL5624186-113959

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Balance Type:	credit
Period Type:	duration