Fair value of derivative liability, presented on a gross basis even when the derivative instrument is subject to master netting arrangements and qualifies for net presentation in the statement of financial position.

Reference 1: 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=6935481&loc=SL5624163-113959

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

-Publisher FASB

-Name Statement of Financial Accounting Standard (FAS)

-Number 133

-Paragraph 44C

-Subparagraph a

-Clause 1

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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 Statement of Financial Accounting Standard (FAS)

-Number 133

-Paragraph 205G

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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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Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

Derivative Financial Instruments (Derivatives And Hedging-Designated) (Details) (NYMEX Commodity Contracts [Member], USD $) In Thousands	Sep. 30, 2011	Dec. 31, 2010
Derivatives, Fair Value [Line Items]
Liability derivatives	$ 38,200
Energy Commodity Derivatives Contracts, Net [Member] \| Designated As Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Asset derivatives	8,689
Liability derivatives
Other Noncurrent Liabilities [Member] \| Designated As Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Liability derivatives		4,920
Other Noncurrent Assets [Member] \| Designated As Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Asset derivatives	1,030
Designated As Hedging Instrument [Member]
Derivatives, Fair Value [Line Items]
Asset derivatives	9,719
Liability derivatives