Goodwill and Intangibles (Goodwill) (Details) $ in Millions	3 Months Ended
	Mar. 31, 2020 USD ($)
Goodwill [Roll Forward]
Balance at January 1, 2020	$ 3,270
Impairments	(1,845)
Balance at March 31, 2020	1,425
Midstream
Goodwill [Roll Forward]
Balance at January 1, 2020	626
Impairments	0
Balance at March 31, 2020	626
Refining
Goodwill [Roll Forward]
Balance at January 1, 2020	1,845
Impairments	(1,845)
Balance at March 31, 2020	0
M&S
Goodwill [Roll Forward]
Balance at January 1, 2020	799
Impairments	0
Balance at March 31, 2020	$ 799