Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Statement of Comprehensive Income [Abstract]
Net income	$ 1,367	$ 1,235	$ 1,626	$ 1,470
Defined benefit plans:
Actuarial changes, net of tax of $0, $2, $6 and $5, respectively	(1)	7	(4)	14
Prior service costs, net of tax of ($3), ($2), ($11) and ($4), respectively	(8)	(7)	(11)	(14)
Other, net of tax of ($1), $0, ($1) and ($1), respectively	(1)	0	(2)	(2)
Other comprehensive income (loss)	(10)	0	(17)	(2)
Comprehensive income	1,357	1,235	1,609	1,468
Less comprehensive income attributable to:
Redeemable noncontrolling interest	21	20	41	36
Noncontrolling interests	240	160	486	342
Comprehensive income attributable to MPC	$ 1,096	$ 1,055	$ 1,082	$ 1,090