Summary Of Significant Accounting Policies (Oil Entitlement Liabilities And Gas Entitlement Assets And Liabilities) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011 MMcf	Dec. 31, 2010 MMcf MBbls
Summary Of Significant Accounting Policies [Abstract]
Oil entitlement liabilities, Amount		$ 1.2
Gas entitlement assets, Amount	7.6	7.6
Gas entitlement liabilities, Amount	$ 2.6	$ 1.6
Oil entitlement liabilities (volumes in MBbls)		13
Gas entitlement assets (volumes in MMcf)	3,024	3,015
Gas entitlement liabilities (volumes in MMcf)	650	439