Segment Information (Reconciliation Of Segment Income From Operations To Income Before Income Taxes) (Detail) - USD ($) $ in Millions	3 Months Ended				9 Months Ended				12 Months Ended
	Sep. 30, 2021		Sep. 30, 2020		Sep. 30, 2021		Sep. 30, 2020		Dec. 31, 2020
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Income (loss) from operations	$ 1,340		$ (1,057)		$ 2,522		$ (12,637)
LCM inventory valuation adjustment	0		(530)		0		1,185
Impairments	13		433		69		9,595
Restructuring expenses	0		348		0		348		$ 367
Net interest and other financial costs	328		359		1,053		1,032
Income before income taxes	1,012		(1,416)		1,469		(13,669)
Operating Segments
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Income (loss) from operations	1,551		(609)		3,126		(876)
Operating Segments | Refining & Marketing
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Income (loss) from operations	509		(1,569)		135		(3,610)
Operating Segments | Midstream
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Income (loss) from operations	1,042		960		2,991		2,734
Corporate
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Income (loss) from operations	(186)		(197)		(523)		(625)
Segment Reconciling Items
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
LCM inventory valuation adjustment	0		530		0		(1,185)
Impairments	(13)		(433)	[1]	(69)	[1]	(9,595)	[1]
Idling expenses	(12)	[1]	0		(12)		0
Restructuring expenses	0		(348)	[2]	0		(348)	[2]
Transaction-related costs	$ 0		$ 0		$ 0		$ (8)	[3]

[1] Includes impairment of goodwill, equity method investments and long lived assets. See Note 6 for additional information.

[2] See Note 16.

[3] Includes costs incurred in connection with the Midstream strategic review. Costs incurred in connection with the Speedway separation are included in discontinued operations. See Note 4.