Derivatives (Gain Or Loss Of Reclassified Accumulated Other Comprehensive Income And Recognized In Income) (Details) (Commodity Derivatives [Member], USD $) In Thousands, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2013		Jun. 30, 2012		Jun. 30, 2013		Jun. 30, 2012
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain or (loss) reclassified from accumulated OCI into income	$ (823)		$ 15,670		$ 3,008		$ 23,846
Derivative Instruments, Gain Recognized in Income	1,717		1,387		368		(606)
Oil and natural gas revenue [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain or (loss) reclassified from accumulated OCI into income	(823)	[1]	15,670	[1]	3,008	[1]	23,846	[1]
Derivative Instruments, Gain Recognized in Income	0		0		0		0
Gain (loss) on derivatives not designated as hedges and hedge ineffectiveness, net [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain or (loss) reclassified from accumulated OCI into income	0		0		0		0
Derivative Instruments, Gain Recognized in Income	$ 1,717	[2]	$ 1,387	[2]	$ 368	[2]	$ (606)	[2]

[1] Effective portion of gain (loss).

[2] Ineffective portion of gain (loss).