Represents the number of counterparties to the entity's commodity derivative contracts.

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- Definition

Represents the number of counterparties with which the entity is in a net liability position for the derivative instruments.

+ Details

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- Definition

Represents the number of major counterparties in terms of the fair value of total net liabilities that account for the specified percentage of the value of its total derivative positions.

+ Details

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- Definition

The maximum amount of loss due to credit risk that the Company would have incurred if all counterparties to its derivative contracts failed to perform at the reporting date.

+ Details

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Period Type:	instant

- Definition

The percentage of the Company's derivative value held by its major counterparties.

+ Details

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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ Details

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- Definition

The effective portion of net gain (loss) reclassified from accumulated other comprehensive income into income on derivative instruments designated and qualifying 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 44C
-Subparagraph b
-Clause 4
-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009.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 4C
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=6935481&loc=SL5624171-113959

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4D
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=6935481&loc=SL5624177-113959

Reference 4: 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.

+ Details

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- Definition

The amount of net gains and losses recognized in income during the period on derivative instruments designated and qualifying as hedging instruments in fair value hedges and related hedged items designated and qualifying in fair value hedges, on derivative instruments designated and qualifying as hedging instruments in cash flow hedges, and on derivative instruments 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 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.

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4A
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=6935481&loc=SL5618551-113959

Reference 3: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4C
-Subparagraph (a),(c),(d),(e)
-URI http://asc.fasb.org/extlink&oid=6935481&loc=SL5624171-113959

Reference 4: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 133
-Paragraph 44C
-Subparagraph b
-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.

+ Details

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

- Definition

The aggregate fair value amounts of derivative instruments that contain credit-risk-related contingent features that are in a net liability position at the end of the reporting period. For nonderivative instruments that are designated and qualify as hedging instruments, the fair value amounts are the carrying value of the nonderivative hedging instrument, including the adjustment for the foreign currency transaction gain (loss) on that instrument.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 815
-SubTopic 10
-Section 50
-Paragraph 4H
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=6935481&loc=SL5624258-113959

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Statement of Financial Accounting Standard (FAS)
-Number 133
-Paragraph 44D
-Subparagraph b
-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.

+ Details

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Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

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Derivative Instruments (Details 3) (USD $)	3 Months Ended		6 Months Ended
Derivative Instruments (Details 3) (USD $)	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Location and the amount of derivative instrument gains (losses) before income taxes recognized in the condensed statements of income
(Gain) loss recognized in earnings (cash settlements and mark-to-market movements)	$ (91,808,000)	$ (56,057,000)	$ 35,708,000	$ (57,661,000)
Credit risk
Maximum loss if all counterparties to its derivative contracts failed to perform	4,500,000		4,500,000
Number of counterparties to the Company's commodity derivative contracts			9
Number of counterparties with net liability position	7		7
Derivative instruments, net liability position	107,000,000		107,000,000
Derivative instruments, number of major counterparties			3
Derivative value held by major counterparties (as a percent)			59.00%
Commodity contract \| Sales of oil and gas
Location and the amount of derivative instrument gains (losses) before income taxes recognized in the condensed statements of income
(Gain) loss reclassified from AOCL into earnings (amortization of frozen amounts)	14,900,000	4,100,000	29,500,000	6,900,000
Commodity contract \| Realized and unrealized gain (loss) on derivatives, net
Location and the amount of derivative instrument gains (losses) before income taxes recognized in the condensed statements of income
(Gain) loss recognized in earnings (cash settlements and mark-to-market movements)	(91,800,000)	(58,800,000)	35,700,000	(63,700,000)
Interest rate contract \| Realized and unrealized gain (loss) on derivatives, net
Location and the amount of derivative instrument gains (losses) before income taxes recognized in the condensed statements of income
(Gain) loss recognized in earnings (cash settlements and mark-to-market movements)		2,700,000		6,000,000
Interest rate contract \| Interest
Location and the amount of derivative instrument gains (losses) before income taxes recognized in the condensed statements of income
(Gain) loss reclassified from AOCL into earnings (amortization of frozen amounts)	$ 400,000	$ 2,400,000	$ 1,200,000	$ 5,100,000