Derivative And Hedging Activities (Components Of Natural Gas And Oil Sales) (Details) (USD $) In Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2011	Jun. 30, 2010	Jun. 30, 2011	Jun. 30, 2010
Derivative And Hedging Activities
Natural gas and oil sales	$ 1,278	$ 984	$ 2,465	$ 2,169
Gains (losses) on natural gas and oil derivatives	506	195	(197)	914
Gains (losses) on ineffectiveness of cash flow hedges	8	(18)	18	(24)
Total natural gas and oil sales	$ 1,792	$ 1,161	$ 2,286	$ 3,059