Derivative Financial Instruments (Schedule Of Derivative Obligations Under Terminated Hedge Arrangements) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Derivative [Line Items]
Amount of Gain/(Loss) Reclassified from AOCI into Earnings	$ (2,347)	$ 8,139	$ (4,855)	$ 16,195
Amount of Gain (Loss) Recognized in Earnings on Derivatives	275,812	229,478	367,562	(14,954)
Interest Rate Derivatives [Member] | Interest Expense [Member]
Derivative [Line Items]
Amount of Gain/(Loss) Reclassified from AOCI into Earnings	0	(69)	(1,699)	(137)
Interest Rate Derivatives [Member] | Derivative Gains, Net [Member]
Derivative [Line Items]
Amount of Gain (Loss) Recognized in Earnings on Derivatives	(22,659)	14,575	(19,039)	12,423
Commodity Price Derivatives [Member] | Derivative Gains, Net [Member]
Derivative [Line Items]
Amount of Gain (Loss) Recognized in Earnings on Derivatives	298,471	214,903	386,601	(27,377)
Commodity Price Derivatives [Member] | Oil And Gas revenue [Member]
Derivative [Line Items]
Amount of Gain/(Loss) Reclassified from AOCI into Earnings	$ (2,347)	$ 8,208	$ (3,156)	$ 16,332