Acquisitions And Divestitures (Summary Of Consideration Paid And Fair Value Of Assets Acquired And Liabilities Assumed) (Details) - USD ($) $ in Millions	1 Months Ended
	Jan. 31, 2015	Dec. 31, 2014
WPX Property Acquisition [Member]
Business Acquisition [Line Items]
Cash	$ 270
Proved natural gas and oil properties	31
Unproved natural gas and oil properties	114
Intangible asset	109
Gathering system	22
Other	1
Total assets acquired	277
Asset retirement obligations	(7)
Total liabilities assumed	(7)
Total assets acquired and liabilities assumed	$ 270
Chesapeake Property Acquisition [Member]
Business Acquisition [Line Items]
Cash		$ 4,949
Proved natural gas and oil properties		1,418
Unproved natural gas and oil properties		3,573
Other property and equipment		33
Inventory		3
Total assets acquired		5,027
Asset retirement obligations		(42)
Other liabilities		(36)
Total liabilities assumed		(78)
Total assets acquired and liabilities assumed		$ 4,949