Derivative Financial Instruments (Schedule Of Derivative Instruments) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012		Dec. 31, 2011
Derivative [Line Items]
Total derivatives, Asset	$ 564,209	[1]	$ 506,177	[1]
Total derivatives, Liability	162,056	[1]	132,078	[1]
Not Designated As Hedging Instruments [Member] | Commodity Price Derivatives [Member] | Derivatives - Current [Member]
Derivative [Line Items]
Total derivatives, Asset	290,366	[1]	248,809	[1]
Total derivatives, Liability	82,365	[1]	68,735	[1]
Not Designated As Hedging Instruments [Member] | Commodity Price Derivatives [Member] | Derivatives - Noncurrent [Member]
Derivative [Line Items]
Total derivatives, Asset	273,843	[1]	257,368	[1]
Total derivatives, Liability	67,657	[1]	47,689	[1]
Not Designated As Hedging Instruments [Member] | Interest Rate Derivatives [Member] | Derivatives - Current [Member]
Derivative [Line Items]
Total derivatives, Liability			15,654	[1]
Not Designated As Hedging Instruments [Member] | Interest Rate Derivatives [Member] | Derivatives - Noncurrent [Member]
Derivative [Line Items]
Total derivatives, Liability	$ 12,034	[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.