Goodwill (Changes In Carrying Amount Of Goodwill) (Detail) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2018	Dec. 31, 2017
Goodwill [Line Items]
Beginning balance		$ 3,586	$ 3,587
Disposition			(1)
Acquisitions		16,598
Transfer of assets related to dropdowns		0
Ending balance		20,184	3,586
Refining & Marketing
Goodwill [Line Items]
Beginning balance		519	519
Disposition			0
Acquisitions		4,717
Transfer of assets related to dropdowns		(216)
Ending balance		5,020	519
Retail
Goodwill [Line Items]
Beginning balance		791	792
Disposition			(1)
Acquisitions	[1]	4,050
Transfer of assets related to dropdowns	[1]	0
Ending balance		4,841	791
Midstream
Goodwill [Line Items]
Beginning balance		2,276	2,276
Disposition			0
Acquisitions		7,831
Transfer of assets related to dropdowns		216
Ending balance		$ 10,323	$ 2,276

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