Financial Instruments (Details 2) (USD $) In Thousands	3 Months Ended	9 Months Ended
Sep. 30, 2011	Sep. 30, 2010	Sep. 30, 2011	Sep. 30, 2010
Reconciliation of changes in the fair value of derivatives classified as Level 3 in the fair value hierarchy
Assets balance, beginning of period	$ 12,327	$ 58,419	$ 14,912	$ 42,606
Total gains or losses:
Non-cash amortization of option premium	(7,443)	(8,163)	(22,069)	(24,210)
Other amounts included in earnings	(529)	10,762	(4,838)	27,615
Included in accumulated other comprehensive loss	17,702	(20,827)	20,176	(78)
Purchases	1,561	3,366	10,725	14,173
Settlements	2,881	(11,134)	7,593	(27,683)
Assets balance, end of period	26,499	32,423	26,499	32,423
Change in unrealized (income) loss included in earnings related to instruments still held as of the end of the period	(448)	181	(703)	305
Natural Gas [Member]
Reconciliation of changes in the fair value of derivatives classified as Level 3 in the fair value hierarchy
Assets balance, beginning of period	4	653	87	2,752
Total gains or losses:
Non-cash amortization of option premium	(1,486)	(1,489)	(4,409)	(4,417)
Included in accumulated other comprehensive loss	1,482	954	4,322	1,783
Assets balance, end of period	0	118	0	118
Natural Gas Liquids [Member]
Reconciliation of changes in the fair value of derivatives classified as Level 3 in the fair value hierarchy
Assets balance, beginning of period	7,043	36,237	8,350	15,641
Total gains or losses:
Non-cash amortization of option premium	(3,953)	(4,154)	(11,714)	(12,317)
Other amounts included in earnings	(2,112)	5,699	(7,211)	12,332
Included in accumulated other comprehensive loss	7,768	(15,048)	7,245	6,208
Purchases	1,561	2,051	8,925	9,433
Settlements	2,881	(5,752)	7,593	(12,264)
Assets balance, end of period	13,188	19,033	13,188	19,033
Change in unrealized (income) loss included in earnings related to instruments still held as of the end of the period	(181)	(135)	(495)	(165)
Crude Oil [Member]
Reconciliation of changes in the fair value of derivatives classified as Level 3 in the fair value hierarchy
Assets balance, beginning of period	5,280	21,529	6,475	24,213
Total gains or losses:
Non-cash amortization of option premium	(2,004)	(2,520)	(5,946)	(7,476)
Other amounts included in earnings	1,583	5,063	2,373	15,283
Included in accumulated other comprehensive loss	8,452	(6,733)	8,609	(8,069)
Purchases		1,315	1,800	4,740
Settlements		(5,382)		(15,419)
Assets balance, end of period	13,311	13,272	13,311	13,272
Change in unrealized (income) loss included in earnings related to instruments still held as of the end of the period	$ (267)	$ 316	$ (208)	$ 470

Fair Value Measurement with unobservable inputs reconciliation recurring basis asset Non cash amortization of option premium.

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Total gains or losses.

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+ References

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Purchases that have taken place during the period in relation to assets measured at fair value and categorized within Level 3 of the fair value hierarchy.

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Settlements that have taken place during the period in relation to assets measured at fair value and categorized within Level 3 of the fair value hierarchy.

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This element represents an asset measured at fair value using significant unobservable inputs (Level 3) which is required for reconciliation purposes of beginning and ending balances.

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-Publisher FASB

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-Paragraph 32

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