Consolidated Statements of Comprehensive Income (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Statement of Comprehensive Income [Abstract]
Net income	$ 679	$ 173	$ 1,750	$ 1,502
Defined benefit postretirement and post-employment plans:
Actuarial changes, net of tax of ($1), $34, $0 and $169	(2)	57	0	282
Prior service costs, net of tax of ($5), ($5), ($14) and ($14)	(8)	(8)	(24)	(23)
Other comprehensive income (loss)	(10)	49	(24)	259
Comprehensive income	669	222	1,726	1,761
Less comprehensive income attributable to noncontrolling interests	7	5	24	16
Comprehensive income attributable to MPC	$ 662	$ 217	$ 1,702	$ 1,745