Segment Information - Reconciliation Of Segment Capital Expenditures And Investments To Total Capital Expenditures (Detail) - USD ($) $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Plus items not allocated to segments:
Capital expenditures	[1]	$ 1,132	$ 841	$ 2,138	$ 1,548
Operating Segments
Reconciliation Of Segment Capital Expenditures And Investments To Total Capital Expenditures [Line Items]
Capital expenditures and investments	[2]	1,364	885	2,654	1,597
Less investments in equity method investees		270	77	595	118
Corporate and Other
Plus items not allocated to segments:
Corporate		4	17	14	35
Capitalized interest		$ 34	$ 16	$ 65	$ 34

[1] Capital expenditures include changes in capital accruals. See Note 19 for a reconciliation of total capital expenditures to additions to property, plant and equipment for the six months ended June 30, 2019 and 2018 as reported in the consolidated statements of cash flows.

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