Supplementary Statistics - Supplementary Statistics (Detail) - USD ($) $ in Millions		3 Months Ended			9 Months Ended
		Sep. 30, 2018		Sep. 30, 2017	Sep. 30, 2018		Sep. 30, 2017
Supplementary Statistics [Line Items]
Income from operations		$ 1,403		$ 1,577	$ 3,554		$ 2,850
Capital expenditures and investments	[1]	945		761	2,611		2,150
Refining & Marketing | Refining Logistics & Fuels Distribution [Member]
Supplementary Statistics [Line Items]
Income from operations		(230)			(643)
Midstream | Refining Logistics & Fuels Distribution [Member]
Supplementary Statistics [Line Items]
Income from operations		230			643
Operating Segments
Supplementary Statistics [Line Items]
Income from operations		1,506		1,660	3,836		3,166
Capital expenditures and investments	[2]	917		729	2,514		2,058
Operating Segments | Refining & Marketing
Supplementary Statistics [Line Items]
Income from operations		666	[3]	1,097	1,558	[3]	1,589
Capital expenditures and investments		226		198	613		570
Operating Segments | Speedway
Supplementary Statistics [Line Items]
Income from operations		161		208	415		581
Capital expenditures and investments		98		108	225		221
Operating Segments | Midstream
Supplementary Statistics [Line Items]
Income from operations		679	[3]	355	1,863	[3]	996
Capital expenditures and investments		593		423	1,676		1,267
Corporate and Other
Supplementary Statistics [Line Items]
Income from operations	[4]	(103)		(85)	(283)		(251)
Capital expenditures and investments	[5]	28		32	97		92
Capitalized interest		21		13	55		39
Segment Reconciling Items
Supplementary Statistics [Line Items]
Litigation		0		0	0		(86)
Impairments	[6]	$ 0		$ 2	$ 1		$ 21

[1] Capital expenditures include changes in capital accruals and investments in affiliates and excludes acquisitions.

[2] Capital expenditures include changes in capital accruals and investments in affiliates. See reconciliation from segment totals to MPC total capital expenditures below.

[3] On February 1, 2018, we contributed certain refining logistics assets and fuels distributions services to MPLX. The results of these new businesses are reported in the Midstream segment prospectively from February 1, resulting in a net reduction of $230 million and $643 million to Refining & Marketing segment results and a net increase to Midstream segment results of the same amount for the three and nine months ended September 30, 2018, respectively. No effect was given to prior periods as these entities were not considered businesses prior to February 1, 2018.

[4] Corporate and other unallocated items consists primarily of MPC’s corporate administrative expenses and costs related to certain non-operating assets, except for corporate overhead expenses attributable to MPLX, which are included in the Midstream segment. Corporate overhead expenses are not allocated to the Refining & Marketing and Speedway segments.

[5] Includes capitalized interest of $21 million and $13 million for the three months ended September 30, 2018 and 2017, respectively, and $55 million and $39 million for the nine months ended September 30, 2018 and 2017, respectively.

[6] Includes MPC’s share of gains from the sale of assets remaining from the canceled Sandpiper pipeline project