Derivative Instruments And Hedging Activities (Narrative) (Details) (USD $) In Millions, unless otherwise specified	1 Months Ended	3 Months Ended		9 Months Ended
	Aug. 31, 2011	Sep. 30, 2010 bbl	Jun. 30, 2010 bbl	Sep. 30, 2011 cf bbl
Derivative Instruments And Hedging Activities
Contracts no longer qualified for hedge accounting oil volume		480,000	480,000
Total volume of oil units				4,500,000
Total volume of natural gas units				8,100,000,000
Term loans payable	$ 200			$ 200
Contract maturity period	January 2014			January 2012
Additional interest rate swap contracts, beginning period	January 2012