Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Statement of Comprehensive Income [Abstract]
Net income	$ 3,255	$ 3,606	$ 3,804
Defined benefit plans:
Actuarial changes, net of tax of ($40), $14 and $17, respectively	(147)	75	29
Prior service credit, net of tax of ($17), $12 and ($16), respectively	(27)	8	(26)
Other, net of tax of ($1), $1 and $0, respectively	(2)	4	0
Other comprehensive income (loss)	(176)	87	3
Comprehensive income	3,079	3,693	3,807
Less comprehensive income attributable to:
Redeemable noncontrolling interest	81	75	65
Noncontrolling interests	537	751	307
Comprehensive income attributable to MPC	$ 2,461	$ 2,867	$ 3,435