Consolidated Statements of Comprehensive Income (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Statement of Comprehensive Income [Abstract]
Net income	$ 2,555	$ 2,133	$ 3,393
Defined benefit postretirement and post-employment plans:
Actuarial changes, net of tax of ($47), $174 and $47	(78)	294	78
Prior service costs, net of tax of ($19), ($19) and $203	(31)	(34)	337
Other comprehensive income (loss)	(109)	260	415
Comprehensive income	2,446	2,393	3,808
Less comprehensive income attributable to noncontrolling interests	31	21	4
Comprehensive income attributable to MPC	$ 2,415	$ 2,372	$ 3,804