Derivative Activities (Details Textuals) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Derivative Activities (Textuals) [Abstract]
Hedged gas swaps (in bcf)			3,100,000
Hedged NGL swaps			25.6
Hedged gas collars (in bcf)	189.1		189.1
Hedged oil collars	700,000		700,000
Hedged oil call options	2,700,000		2,700,000
Average price of oil call option (per barrel)	$ 83.15		$ 83.15
Derivative assets liabilities at fair value net	61,100,000		61,100,000
Unrealized pre-tax derivative gain			73,500,000
Gains (Losses) in oil and gas sales related to settled hedging transactions	24,300,000	18,300,000	53,900,000	19,600,000
Ineffective unrealized and realized gains (losses) recognized income	7,510,000	265,000	9,024,000	(341,000)
Gains/losses recorded due to the discontinuance of hedge accounting treatment	0	0	0	0
Number of financial institutions with whom we conduct derivative activities			10
Number of secured financial institutions with whom we conduct derivative activities			9
Collar Oil [Member]
Derivative [Line Items]
Average floor price	70.00		70.00
Average cap price	80.00		80.00
Natural Gas [Member]
Derivative [Line Items]
Average floor price	5.27		5.27
Average cap price	5.93		5.93
Average price of SWAP per mcf	5.00		5.00
NGL [Member]
Derivative [Line Items]
Average price of SWAP per mcf	103.24		103.24
2011 [Member]
Derivative [Line Items]
Unrealized pre-tax derivative gain expected to be reclassified into earnings			44,100,000
2012 [Member]
Derivative [Line Items]
Unrealized pre-tax derivative gain expected to be reclassified into earnings			21,900,000
2013 [Member]
Derivative [Line Items]
Unrealized pre-tax derivative gain expected to be reclassified into earnings			$ 7,500,000