Derivative Financial Instruments (Fair Value Of Oil And Natural Gas Derivative Financial Instruments) (Details) (USD $) In Thousands, except Per Share data, unless otherwise specified	Apr. 30, 2012	Mar. 31, 2012	Dec. 31, 2011
Derivatives, Fair Value [Line Items]
Weighted average strike price per Mmbtu/Bbl	4.18
Total oil and natural gas and derivatives, fair value at march 31, 2012		$ 176,956	$ 173,236
Swaps [Member]
Derivatives, Fair Value [Line Items]
Total oil and natural gas and derivatives, fair value at march 31, 2012		176,956
Swaps [Member] | Natural Gas [Member]
Derivatives, Fair Value [Line Items]
Volume Mmbtus/Bbls		65,975
Total oil and natural gas and derivatives, fair value at march 31, 2012		180,930
Swaps [Member] | Oil [Member]
Derivatives, Fair Value [Line Items]
Volume Mmbtus/Bbls		778
Total oil and natural gas and derivatives, fair value at march 31, 2012		(3,974)
Remainder Of 2012 [Member] | Swaps [Member] | Natural Gas [Member]
Derivatives, Fair Value [Line Items]
Volume Mmbtus/Bbls		60,500
Weighted average strike price per Mmbtu/Bbl		$ 5.27
Total oil and natural gas and derivatives, fair value at march 31, 2012		167,304
Remainder Of 2012 [Member] | Swaps [Member] | Oil [Member]
Derivatives, Fair Value [Line Items]
Volume Mmbtus/Bbls		413
Weighted average strike price per Mmbtu/Bbl		$ 98.05
Total oil and natural gas and derivatives, fair value at march 31, 2012		(2,666)
2013 [Member] | Swaps [Member] | Natural Gas [Member]
Derivatives, Fair Value [Line Items]
Volume Mmbtus/Bbls		5,475
Weighted average strike price per Mmbtu/Bbl		$ 5.99
Total oil and natural gas and derivatives, fair value at march 31, 2012		13,626
2013 [Member] | Swaps [Member] | Oil [Member]
Derivatives, Fair Value [Line Items]
Volume Mmbtus/Bbls		365
Weighted average strike price per Mmbtu/Bbl		$ 99.96
Total oil and natural gas and derivatives, fair value at march 31, 2012		$ (1,308)