Segment Information - Income From Operations Attributable To Operating Segments (Detail) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Segment Reporting Information [Line Items]
Sales and other operating revenues		$ 33,547	$ 22,317	$ 61,814	$ 41,183
Income from operations		2,042	1,711	2,711	2,151
Depreciation and amortization		886	533	1,805	1,061
Intersegment Eliminations
Segment Reporting Information [Line Items]
Sales and other operating revenues		6,702	3,635	12,365	6,646
Operating Segments
Segment Reporting Information [Line Items]
Sales and other operating revenues		40,249	25,952	74,179	47,829
Income from operations		2,277	1,801	3,021	2,330
Depreciation and amortization	[1]	859	516	1,719	1,028
Capital expenditures and investments	[2]	1,364	885	2,654	1,597
Refining & Marketing
Segment Reporting Information [Line Items]
Sales and other operating revenues		23,672	16,302	43,606	29,884
Refining & Marketing | Intersegment Eliminations
Segment Reporting Information [Line Items]
Sales and other operating revenues		5,482	2,871	9,911	5,250
Refining & Marketing | Operating Segments
Segment Reporting Information [Line Items]
Sales and other operating revenues		29,154	19,173	53,517	35,134
Income from operations		906	1,025	572	892
Depreciation and amortization		411	252	838	504
Capital expenditures and investments		430	196	824	387
Retail
Segment Reporting Information [Line Items]
Sales and other operating revenues		8,944	5,265	16,320	9,836
Retail | Intersegment Eliminations
Segment Reporting Information [Line Items]
Sales and other operating revenues		2	2	4	3
Retail | Operating Segments
Segment Reporting Information [Line Items]
Sales and other operating revenues		8,946	5,267	16,324	9,839
Income from operations		493	159	663	254
Depreciation and amortization		130	73	256	152
Capital expenditures and investments		120	88	193	127
Midstream
Segment Reporting Information [Line Items]
Sales and other operating revenues		931	750	1,888	1,463
Midstream | Intersegment Eliminations
Segment Reporting Information [Line Items]
Sales and other operating revenues		1,218	762	2,450	1,393
Midstream | Operating Segments
Segment Reporting Information [Line Items]
Sales and other operating revenues		2,149	1,512	4,338	2,856
Income from operations		878	617	1,786	1,184
Depreciation and amortization		318	191	625	372
Capital expenditures and investments		814	601	1,637	1,083
Reportable Segment
Segment Reporting Information [Line Items]
Sales and other operating revenues	[3]	$ 33,547	$ 22,317	$ 61,814	$ 41,183

[1] Differences between segment totals and MPC consolidated totals represent amounts related to corporate and other unallocated items and are included in items not allocated to segments in the reconciliation below.

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

[3] Includes related party sales. See Note 6 for additional information.