MPLX LP (Noncontrolling Interest) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Impact from equity transactions of MPLX	$ 658	$ 6,923	$ 221
Additional Paid-in Capital
Increase (decrease) in MPC's paid in capital for the issuance of MPLX LP common units to the public	(60)	1,532
Increase in MPC's paid in capital for the issuance of MPLX LP common units and general partner units to MPC	121	0
Net transfers (to) from noncontrolling interests	61	1,532
Tax impact	(118)	(404)
Impact from equity transactions of MPLX	$ (57)	$ 1,128