Derivatives (Effect Of Derivative Instruments Recognized In Statement Of Operations, Derivative Instruments) (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2016	Mar. 31, 2015
Derivative Instruments, Gain (Loss) [Line Items]
Gain on derivatives		$ 10,929	$ 6,586
Commodity Derivatives [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain on derivatives		10,929	6,586
Amount of gain settled during the period		7,100	11,000
Gain on derivatives [Member] | Commodity Derivatives [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain on derivatives	[1]	$ 10,929	$ 6,586

[1] Amounts settled during the 2016 and 2015 periods include gains of $7.1 million and $11.0 million, respectively.