Derivatives (Gain Or Loss Of Reclassified Accumulated Other Comprehensive Income And Recognized In Income) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013		Mar. 31, 2012
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain Reclassified from Accumulated OCI into Income	$ 3,831		$ 8,176
Commodity Derivatives [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain or (Loss) Recognized in Income	(1,349)		(1,993)
Loss on Derivatives [Member] | Commodity Derivatives [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain Reclassified from Accumulated OCI into Income	0		0
Amount of Gain or (Loss) Recognized in Income	(1,349)	[1]	(1,993)	[1]
Oil And Natural Gas Revenue [Member] | Commodity Derivatives [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of Gain Reclassified from Accumulated OCI into Income	3,831	[2]	8,176	[2]
Amount of Gain or (Loss) Recognized in Income	$ 0		$ 0

[1] Ineffective portion of gain (loss).

[2] Effective portion of gain (loss).