DERIVATIVE INSTRUMENTS (Details 2) (USD $) In Thousands	Jun. 30, 2011	Dec. 31, 2010
Derivative contracts not designated as hedging instruments and their balance sheet location
Total assets	$ 70,949	$ 68,426
Total liabilities	47,818	36,413
Net derivative fair value	23,131	32,013
Current assets
Derivative contracts not designated as hedging instruments and their balance sheet location
Commodity derivative asset	41,713	49,415
Interest rate derivatives asset	10,894	10,767
Noncurrent assets
Derivative contracts not designated as hedging instruments and their balance sheet location
Commodity derivative asset	8,463
Interest rate derivatives asset	9,879	8,244
Current liabilities
Derivative contracts not designated as hedging instruments and their balance sheet location
Commodity derivative liability	42,428	36,413
Noncurrent liabilities
Derivative contracts not designated as hedging instruments and their balance sheet location
Commodity derivative liability	$ 5,390

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

Reference 1: 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-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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.

Reference 2: 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=6935481&loc=SL5624163-113959

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Fair value as of the balance sheet date of all derivative assets not designated as hedging instruments.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 133
-Paragraph 17
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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 Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4B
-Subparagraph (c)(2)
-URI http://asc.fasb.org/extlink&oid=6935481&loc=SL5624163-113959

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Net fair value of all derivative instruments not designated as a hedging instrument.

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Reference 1: 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.

Reference 2: 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=6947722&loc=d3e13433-108611

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-Name Accounting Standards Codification
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-SubTopic 10
-Section 50
-Paragraph 15
-URI http://asc.fasb.org/extlink&oid=6947722&loc=d3e13495-108611

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