Supplementary Statistics - Supplementary Statistics (Detail) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2016		Mar. 31, 2015
Supplementary Statistics [Line Items]
Income from operations		$ 75		$ 1,470
Impairment expense		129		0
Capital expenditures and investments	[1],[2]	684		384
Refining & Marketing
Supplementary Statistics [Line Items]
Impairment expense		0
Speedway
Supplementary Statistics [Line Items]
Impairment expense		0
Midstream
Supplementary Statistics [Line Items]
Impairment expense		129
Operating Segments
Supplementary Statistics [Line Items]
Income from operations	[3]	272		1,550
Capital expenditures and investments	[4]	643		355
Operating Segments | Refining & Marketing
Supplementary Statistics [Line Items]
Income from operations	[5]	(62)		1,292
Capital expenditures and investments	[5]	243		223
Operating Segments | Speedway
Supplementary Statistics [Line Items]
Income from operations		167		168
Capital expenditures and investments		50		45
Operating Segments | Midstream
Supplementary Statistics [Line Items]
Income from operations	[3],[5]	167		90
Capital expenditures and investments	[5]	350		87
Corporate and Other
Supplementary Statistics [Line Items]
Income from operations	[5],[6],[7]	(67)		(79)
Capital expenditures and investments	[2]	41		29
Capitalized interest		17		8
Segment Reconciling Items
Supplementary Statistics [Line Items]
Pension settlement expenses	[8]	(1)		(1)
Impairment expense		$ (129)	[9]	$ 0

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

[2] Includes capitalized interest of $17 million and $8 million for the three months ended March 31, 2016 and 2015, respectively.

[3] Corporate overhead expenses attributable to MPLX are included in the Midstream segment. Corporate overhead expenses are not allocated to the Refining & Marketing and Speedway segments.

[4] Capital expenditures include changes in capital accruals, acquisitions (including any goodwill) and investments in affiliates.

[5] We revised our operating segment presentation in the first quarter of 2016 in connection with the contribution of our inland marine business to MPLX; our inland marine business, which was previously included in Refining & Marketing, is now included in Midstream. Comparable prior period information has been recast to reflect our revised segment presentation.

[6] Corporate and other unallocated items consists primarily of MPC’s corporate administrative expenses and costs related to certain non-operating assets.

[7] Corporate overhead expenses attributable to MPLX are included in the Midstream segment. Corporate overhead expenses are not allocated to the Refining & Marketing and Speedway segments.

[8] See Note 20.

[9] See Note 14.