Consolidated Statements of Comprehensive Income (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Statement of Comprehensive Income [Abstract]
Net income	$ 864	$ 599	$ 1,071	$ 1,329
Defined benefit postretirement and post-employment plans:
Actuarial changes, net of tax of ($3), $81, $1 and $135	(5)	135	2	225
Prior service costs, net of tax of ($4), ($4), ($9) and ($9)	(8)	(7)	(16)	(15)
Other comprehensive income (loss)	(13)	128	(14)	210
Comprehensive income	851	727	1,057	1,539
Less comprehensive income attributable to noncontrolling interests	9	6	17	11
Comprehensive income attributable to MPC	$ 842	$ 721	$ 1,040	$ 1,528