Derivative Financial Instruments (Fair Value Of Oil And Gas Derivative Financial Instruments) (Details) (Swaps [Member], USD $) In Thousands, except Per Share data, unless otherwise specified	Sep. 30, 2011 bbl
Derivatives, Fair Value [Line Items]
Total oil and natural gas and derivatives	$ 136,812
Remainder Of 2011 [Member] | Natural Gas [Member]
Derivatives, Fair Value [Line Items]
Volume (in Mmbtus/Bbls)	30,820
Weighted average strike price (in Mmbtu/Bbl)	$ 5.17
Total oil and natural gas and derivatives	41,408
Remainder Of 2011 [Member] | Oil [Member]
Derivatives, Fair Value [Line Items]
Volume (in Mmbtus/Bbls)	138
Weighted average strike price (in Mmbtu/Bbl)	$ 111.32
Total oil and natural gas and derivatives	4,323
2012 [Member] | Natural Gas [Member]
Derivatives, Fair Value [Line Items]
Volume (in Mmbtus/Bbls)	80,520
Weighted average strike price (in Mmbtu/Bbl)	$ 5.27
Total oil and natural gas and derivatives	80,896
2012 [Member] | Oil [Member]
Derivatives, Fair Value [Line Items]
Volume (in Mmbtus/Bbls)	275
Weighted average strike price (in Mmbtu/Bbl)	$ 95.70
Total oil and natural gas and derivatives	3,884
2013 [Member] | Natural Gas [Member]
Derivatives, Fair Value [Line Items]
Volume (in Mmbtus/Bbls)	5,475
Weighted average strike price (in Mmbtu/Bbl)	$ 5.99
Total oil and natural gas and derivatives	6,301
Natural Gas [Member]
Derivatives, Fair Value [Line Items]
Volume (in Mmbtus/Bbls)	116,815
Total oil and natural gas and derivatives	128,605
Oil [Member]
Derivatives, Fair Value [Line Items]
Volume (in Mmbtus/Bbls)	413
Total oil and natural gas and derivatives	$ 8,207