Master Limited Partnerships - Noncontrolling Interest in MLPs (Details) - USD ($) $ in Millions	3 Months Ended				6 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018
Increase in MPC's additional paid-in capital, net of tax	$ 1	$ 2	$ 0	$ (546)
Additional Paid-in Capital
Increase due to the issuance of MPLX common units and general partner units to MPC					$ 0	$ 1,114
Increase due to GP/IDR Exchange					0	1,808
Increase due to the issuance of MPLX & ANDX common units					7	5
Increase in MPC's additional paid-in capital					7	2,927
Tax impact					(2)	(546)
Increase in MPC's additional paid-in capital, net of tax	$ 2	$ 3	$ 1	$ 2,380	$ 5	$ 2,381