Segment Information - Reconciliation Of Segment Income From Operations To Income Before Income Taxes (Detail) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2016		Mar. 31, 2015
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Income from operations		$ 75		$ 1,470
Impairment expense		129		0
Net interest and other financial income (costs)		142		81
Income before income taxes		(67)		1,389
Operating Segments
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Income from operations	[1]	272		1,550
Corporate and Other
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Income from operations	[2],[3],[4]	(67)		(79)
Segment Reconciling Items
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Pension settlement expenses	[5]	(1)		(1)
Impairment expense		$ (129)	[6]	$ 0

[1] 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.

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

[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] 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.

[5] See Note 20.

[6] See Note 14.