Acquisitions And Divestitures (Narrative) (Detail) - USD ($) shares in Millions, $ in Millions	3 Months Ended
	Mar. 31, 2017	Mar. 31, 2016	Dec. 31, 2016
Business Acquisition [Line Items]
(Gain) loss on disposition of assets, net	$ (654)	$ (111)
Funds held in escrow	0		$ 43
Common stock issued in business combination	258	$ 231
Alpha Crude Connector [Member]
Business Acquisition [Line Items]
Proceeds From Sale Of Oil And Gas Property And Equipment	803
(Gain) loss on disposition of assets, net	(656)
Total equity method investment	129
Northern Delaware Basin [Member]
Business Acquisition [Line Items]
Cash consideration paid for acquisition	$ 132
Common stock issued in business combination (Shares)	1.9
Common stock issued in business combination	$ 258