Derivatives And Fair Value Measurements (Estimated Fair Value Of Derivative Instruments Under Input Levels) (Details) - USD ($) $ in Thousands	Sep. 30, 2015	Dec. 31, 2014
Asset Derivatives [Member]
Derivatives, Fair Value [Line Items]
Estimated fair value of derivative instruments	$ 0	$ 149,567
Asset Derivatives [Member] | Fair Value Inputs, Level 2 [Member] | Commodity Contracts [Member]
Derivatives, Fair Value [Line Items]
Estimated fair value of derivative instruments	0	104,608
Asset Derivatives [Member] | Fair Value Inputs, Level 3 [Member] | Commodity Contracts [Member]
Derivatives, Fair Value [Line Items]
Estimated fair value of derivative instruments	0	44,959
Liability Derivatives [Member]
Derivatives, Fair Value [Line Items]
Estimated fair value of derivative instruments	0	0
Liability Derivatives [Member] | Fair Value Inputs, Level 2 [Member] | Commodity Contracts [Member]
Derivatives, Fair Value [Line Items]
Estimated fair value of derivative instruments	0	0
Liability Derivatives [Member] | Fair Value Inputs, Level 3 [Member] | Commodity Contracts [Member]
Derivatives, Fair Value [Line Items]
Estimated fair value of derivative instruments	$ 0	$ 0