Derivative Financial Instruments (Schedule Of Derivative Instruments) (Details) (Not Designated As Hedging Instruments [Member], USD $) In Thousands, unless otherwise specified	Jun. 30, 2012		Dec. 31, 2011
Derivative [Line Items]
Total derivatives, Asset	$ 589,184	[1]	$ 506,177	[1]
Total derivatives, Liability	67,928	[1]	132,078	[1]
Commodity Price Derivatives [Member] | Derivatives - Current [Member]
Derivative [Line Items]
Total derivatives, Asset	318,503	[1]	248,809	[1]
Total derivatives, Liability	17,108	[1]	68,735	[1]
Commodity Price Derivatives [Member] | Derivatives - Noncurrent [Member]
Derivative [Line Items]
Total derivatives, Asset	270,681	[1]	257,368	[1]
Total derivatives, Liability	16,127	[1]	47,689	[1]
Interest Rate Derivatives [Member] | Derivatives - Current [Member]
Derivative [Line Items]
Total derivatives, Liability	$ 23,283	[1]	$ 15,654	[1]

[1] Derivative assets and liabilities shown in the tables above are presented as gross assets and liabilities, without regard to master netting arrangements which are considered in the presentations of derivative assets and liabilities in the accompanying consolidated balance sheets.