Consolidated Statements of Equity - USD ($)	Total	Preferred Class B [Member]	Public Limited Partners Common Units	MPC Limited Partners Common Units	Accumulated Other Comprehensive Loss	Noncontrolling Interests	Equity of Predecessor MPC
Beginning Balance at Dec. 31, 2018	$ 17,731,000,000	$ 0	$ 8,336,000,000	$ (1,612,000,000)	$ (16,000,000)	$ 156,000,000	$ 10,867,000,000
Distributions to:	(669,000,000)	0	176,000,000	307,000,000	0	(6,000,000)	(180,000,000)
Contributions from:	15,000,000	0	0	0	0	0	15,000,000
Unitholders and general partner	(776,000,000)	0	(188,000,000)	(327,000,000)	0	0	(261,000,000)
Noncontrolling interests	(6,000,000)	0	0	0	0	(6,000,000)	0
Contributions from noncontrolling interests	(94,000,000)	0	0	0	0	(94,000,000)	0
Other	3,000,000	0	2,000,000	0	1,000,000	0	0
Ending Balance at Mar. 31, 2019	17,730,000,000	0	8,326,000,000	(1,632,000,000)	(15,000,000)	250,000,000	10,801,000,000
Beginning Balance at Dec. 31, 2018	17,731,000,000	0	8,336,000,000	(1,612,000,000)	(16,000,000)	156,000,000	10,867,000,000
Contributions from noncontrolling interests	(94,000,000)
Ending Balance at Sep. 30, 2019	17,892,000,000	601,000,000	11,289,000,000	5,767,000,000	(15,000,000)	250,000,000	0
Beginning Balance at Mar. 31, 2019	17,730,000,000	0	8,326,000,000	(1,632,000,000)	(15,000,000)	250,000,000	10,801,000,000
Distributions to:	(636,000,000)	0	168,000,000	293,000,000	0	(6,000,000)	(169,000,000)
Contributions from:	13,000,000	0	0	0	0	0	13,000,000
Unitholders and general partner	(764,000,000)	0	(191,000,000)	(332,000,000)	0	0	241,000,000
Noncontrolling interests	(6,000,000)	0	0	0	0	(6,000,000)	0
Other	2,000,000	0	2,000,000	0	0	0	0
Ending Balance at Jun. 30, 2019	17,611,000,000	0	8,305,000,000	(1,671,000,000)	(15,000,000)	250,000,000	10,742,000,000
Distributions to:	(669,000,000)	(7,000,000)	(222,000,000)	(380,000,000)	0	(8,000,000)	(52,000,000)
Stockholders' Equity, Change in Reporting Entity	0	615,000,000	2,983,000,000	7,199,000,000	0	0	(10,797,000,000)
Contributions from:	295,000,000	0	0	292,000,000	0	0	3,000,000
Unitholders and general partner	(715,000,000)	(21,000,000)	(262,000,000)	(432,000,000)	0	0	0
Noncontrolling interests	(8,000,000)	0	0	0	0	(8,000,000)	0
Partners' Capital Account, Exchanges and Conversions	36,000,000	0	36,000,000	0	0	0	0
Other	4,000,000	0	5,000,000	(1,000,000)	0	0	0
Ending Balance at Sep. 30, 2019	17,892,000,000	601,000,000	11,289,000,000	5,767,000,000	(15,000,000)	250,000,000	0
Beginning Balance at Dec. 31, 2019	16,613,000,000	611,000,000	10,800,000,000	4,968,000,000	(15,000,000)	249,000,000	0
Distributions to:	2,736,000,000	(11,000,000)	(1,022,000,000)	(1,733,000,000)	0	(8,000,000)	0
Contributions from:	225,000,000	0	0	225,000,000	0	0	0
Unitholders and general partner	(738,000,000)	(21,000,000)	(271,000,000)	(446,000,000)	0	0	0
Noncontrolling interests	(9,000,000)	0	0	0	0	(9,000,000)	0
Other	1,000,000	0	2,000,000	0	(1,000,000)	0	0
Ending Balance at Mar. 31, 2020	13,356,000,000	601,000,000	9,509,000,000	3,014,000,000	(16,000,000)	248,000,000	0
Beginning Balance at Dec. 31, 2019	16,613,000,000	611,000,000	10,800,000,000	4,968,000,000	(15,000,000)	249,000,000	0
Distributions to:		(31,000,000)
Unitholders and general partner		(41,000,000)
Contributions from noncontrolling interests	0
Ending Balance at Sep. 30, 2020	13,095,000,000	601,000,000	9,436,000,000	2,827,000,000	(16,000,000)	247,000,000	0
Beginning Balance at Mar. 31, 2020	13,356,000,000	601,000,000	9,509,000,000	3,014,000,000	(16,000,000)	248,000,000	0
Distributions to:	(634,000,000)	(10,000,000)	229,000,000	388,000,000	0	(7,000,000)	0
Contributions from:	6,000,000	0	0	6,000,000	0	0	0
Unitholders and general partner	(728,000,000)	0	(270,000,000)	(458,000,000)	0	0	0
Noncontrolling interests	(8,000,000)	0	0	0	0	(8,000,000)	0
Other	2,000,000	0	1,000,000	1,000,000	0	0	0
Ending Balance at Jun. 30, 2020	13,262,000,000	611,000,000	9,469,000,000	2,951,000,000	(16,000,000)	247,000,000	0
Distributions to:	(654,000,000)	(10,000,000)	236,000,000	399,000,000	0	(9,000,000)	0
Stockholders' Equity, Change in Reporting Entity	(90,000,000)	0	0	(90,000,000)	0	0	0
Contributions from:	13,000,000	0	0	13,000,000	0	0	0
Unitholders and general partner	(736,000,000)	(20,000,000)	(271,000,000)	(445,000,000)	0	0	0
Noncontrolling interests	(9,000,000)	0	0	0	0	(9,000,000)	0
Other	1,000,000	0	2,000,000	(1,000,000)	0	0	0
Ending Balance at Sep. 30, 2020	$ 13,095,000,000	$ 601,000,000	$ 9,436,000,000	$ 2,827,000,000	$ (16,000,000)	$ 247,000,000	$ 0