Segment Information - Reconciliation Of Segment Capital Expenditures And Investments To Total Capital Expenditures (Detail) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2020	Mar. 31, 2019
Plus items not allocated to segments:
Capital expenditures	[1]	$ 896	$ 1,006
Operating Segments
Reconciliation Of Segment Capital Expenditures And Investments To Total Capital Expenditures [Line Items]
Capital expenditures and investments	[2]	1,009	1,290
Less investments in equity method investees		169	325
Corporate and Other
Plus items not allocated to segments:
Corporate		27	10
Capitalized interest		$ 29	$ 31

[1] Includes changes in capital expenditure accruals. See Note 19 for a reconciliation of total capital expenditures to additions to property, plant and equipment for the three months ended March 31, 2020 and 2019 as reported in the consolidated statements of cash flows.

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