Derivative Financial Instruments (Schedule Of Derivative Obligations Under Terminated Hedge Arrangements) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Derivative [Line Items]
Amount of Gain/(Loss) Reclassified from AOCI into Earnings	$ 0	$ 2,508
Derivative (gains) losses, net	42,243	(91,750)
Commodity Price Derivatives [Member] | Oil And Gas revenue [Member]
Derivative [Line Items]
Amount of Gain/(Loss) Reclassified from AOCI into Earnings	0	809
Commodity Price Derivatives [Member] | Derivative Gains, Net [Member]
Derivative [Line Items]
Derivative (gains) losses, net	46,183	(88,130)
Interest Rate Derivatives [Member] | Interest Expense [Member]
Derivative [Line Items]
Amount of Gain/(Loss) Reclassified from AOCI into Earnings	0	1,699
Interest Rate Derivatives [Member] | Derivative Gains, Net [Member]
Derivative [Line Items]
Derivative (gains) losses, net	$ (3,940)	$ (3,620)