Derivatives And Fair Value Measurements (Estimated Fair Value Of Derivative Instruments Under Input Levels) (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Asset Derivatives [Member]
Derivatives, Fair Value [Line Items]
Estimated fair value of derivative instruments	$ 92,066	$ 130,880
Asset Derivatives [Member] | Fair Value Inputs, Level 2 [Member] | Commodity Contracts [Member]
Derivatives, Fair Value [Line Items]
Estimated fair value of derivative instruments	74,312	107,395
Asset Derivatives [Member] | Fair Value Inputs, Level 3 [Member] | Commodity Contracts [Member]
Derivatives, Fair Value [Line Items]
Estimated fair value of derivative instruments	17,754	23,485
Liability Derivatives [Member]
Derivatives, Fair Value [Line Items]
Estimated fair value of derivative instruments	846	3,448
Liability Derivatives [Member] | Fair Value Inputs, Level 2 [Member] | Commodity Contracts [Member]
Derivatives, Fair Value [Line Items]
Estimated fair value of derivative instruments	846	3,448
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