Acquisitions (Summary Of Consideration Paid And Fair Value Of Assets Acquired And Liabilities Assumed) (Details) (Chesapeake Property Acquisition [Member], USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014
Chesapeake Property Acquisition [Member]
Business Acquisition [Line Items]
Cash	$ 4,978
Proved natural gas and oil properties	1,424
Unproved natural gas and oil properties	3,605
Other property and equipment	19
Inventory	2
Other receivables	27
Total assets acquired	5,077
Asset retirement obligations	(42)
Other long-term liabilities	(57)
Total liabilities assumed	(99)
Total assets acquired and liabilities assumed	$ 4,978