(Changes In Carrying Amount Of Goodwill) (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2019	Dec. 31, 2018
Goodwill [Line Items]
Beginning balance	$ 20,184	$ 3,586
Acquisitions	94	16,598
Dropdowns to MPLX		0
Purchase price allocation adjustments	976
Impairments	(1,197)
Dispositions	(17)
Ending balance	20,040	20,184
Refining & Marketing
Goodwill [Line Items]
Beginning balance	5,020	519
Acquisitions	38	4,717
Dropdowns to MPLX		(216)
Purchase price allocation adjustments	514
Impairments	0
Dispositions	0
Ending balance	5,572	5,020
Retail
Goodwill [Line Items]
Beginning balance	4,841	791
Acquisitions	56	4,050
Dropdowns to MPLX		0
Purchase price allocation adjustments	54
Impairments	0
Dispositions	0
Ending balance	4,951	4,841
Midstream
Goodwill [Line Items]
Beginning balance	10,323	2,276
Acquisitions	0	7,831
Dropdowns to MPLX		216
Purchase price allocation adjustments	408
Impairments	(1,197)
Dispositions	(17)
Ending balance	$ 9,517	$ 10,323

Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized.

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