Segment Information - Income From Operations Attributable To Operating Segments (Detail) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2020	Mar. 31, 2019
Segment Reporting Information [Line Items]
Sales and other operating revenues		$ 25,215	$ 28,253
Income from operations		(11,817)	669
Depreciation and amortization		962	919
Intersegment Eliminations
Segment Reporting Information [Line Items]
Sales and other operating revenues		4,861	5,650
Operating Segments
Segment Reporting Information [Line Items]
Sales and other operating revenues		30,076	33,903
Income from operations		802	744
Depreciation and amortization	[1]	917	860
Capital expenditures and investments	[2]	1,009	1,290
Refining & Marketing
Segment Reporting Information [Line Items]
Sales and other operating revenues		17,528	19,920
Refining & Marketing | Intersegment Eliminations
Segment Reporting Information [Line Items]
Sales and other operating revenues		3,617	4,416
Refining & Marketing | Operating Segments
Segment Reporting Information [Line Items]
Sales and other operating revenues		21,145	24,336
Income from operations		(622)	(334)
Depreciation and amortization		447	427
Capital expenditures and investments		459	394
Retail
Segment Reporting Information [Line Items]
Sales and other operating revenues		6,769	7,376
Retail | Intersegment Eliminations
Segment Reporting Information [Line Items]
Sales and other operating revenues		2	2
Retail | Operating Segments
Segment Reporting Information [Line Items]
Sales and other operating revenues		6,771	7,378
Income from operations		519	170
Depreciation and amortization		125	126
Capital expenditures and investments		76	73
Midstream
Segment Reporting Information [Line Items]
Sales and other operating revenues		918	957
Midstream | Intersegment Eliminations
Segment Reporting Information [Line Items]
Sales and other operating revenues		1,242	1,232
Midstream | Operating Segments
Segment Reporting Information [Line Items]
Sales and other operating revenues		2,160	2,189
Income from operations		905	908
Depreciation and amortization		345	307
Capital expenditures and investments		474	823
Reportable Segment
Segment Reporting Information [Line Items]
Sales and other operating revenues	[3]	$ 25,215	$ 28,253

[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] Includes changes in capital expenditure 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.