Acquisitions And Divestitures (Summary Of Consideration Paid And Fair Value Of Assets Acquired And Liabilities Assumed) (Details) - Chesapeake Property Acquisition [Member] $ in Millions	Dec. 22, 2014 USD ($)
Business Acquisition [Line Items]
Cash	$ 4,959
Proved natural gas and oil properties	1,418
Unproved natural gas and oil properties	3,574
Other property and equipment	33
Inventory	3
Total assets acquired	5,028
Asset retirement obligations	(42)
Other liabilities	(27)
Total liabilities assumed	(69)
Total assets acquired and liabilities assumed	$ 4,959