Acquisitions And Divestitures (Narrative) (Detail) - USD ($) shares in Millions, $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2017	Jun. 30, 2016	Jun. 30, 2017	Jun. 30, 2016	Dec. 31, 2016
Business Acquisition [Line Items]
(Gain) loss on disposition of assets, net	$ 0	$ 1	$ (654)	$ (110)
Funds held in escrow	60		60		$ 43
Common stock issued in business combination			291	$ 231
Northern Delaware Basin [Member]
Business Acquisition [Line Items]
Total cash consideration paid for acquisition			$ 159
Funds held in escrow					$ 43
Common stock issued in business combination (Shares)			2.2
Common stock issued in business combination			$ 291
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		$ 129