Consolidated Statements of Equity - USD ($) $ in Millions	Total	Preferred Partner [Member]	Public Limited Partners Common Units	Public Limited Partners Class B Units	MPC Limited Partners Common Units	MPC General Partner	AOCI Attributable to Parent	Noncontrolling Interest	Equity of Predecessor MPC
Beginning balance at Dec. 31, 2016	$ 11,110	$ 0	$ 8,086	$ 133	$ 1,069	$ 1,013	$ 0	$ 18	$ 791
Distributions to MPC from Predecessor	(113)	0	0	0	0	0	0	0	(113)
Distribution declared, general partner	(32)	0	0	0	0	(32)	0	0	0
Contribution from MPC	(675)	0	0	0	0	0	(14)	0	(689)
Unit issuances under ATM Program	483	0	473	0	0	10	0	0	0
Stockholders' Equity, Other	8	0	8	0	0	0	0	0	0
Net income (loss)	(771)	0	(301)	0	(110)	(318)	0	(6)	(36)
Allocation of MPC's net investment at acquisition	0	0	0	0	(1,669)	266	0	0	1,403
Distribution to MPC for acquisitions	(1,931)	0	0	0	(537)	(1,394)	0	0	0
Noncontrolling interests	(1,120)	0	(622)	0	(212)	(286)	0	0	0
(Placeholder)	(7)	0	0	0	0	0	0	(7)	0
Contributions from noncontrolling interests	129	0	0	0	0	0	0	129	0
Unit conversion	0	0	(133)	133	0	0	0	0	0
Ending balance at Dec. 31, 2017	9,973	0	8,379	0	2,099	(637)	(14)	146	0
Distributions to MPC from Predecessor	0
Contribution from MPC	(11,980)	0	0	0	0	0	0	0	(11,980)
Stockholders' Equity, Other	11	0	12	0	0	1	(2)	0	0
Net income (loss)	(1,931)	0	(667)	0	(1,076)	0	0	(16)	(172)
Allocation of MPC's net investment at acquisition	0	0	0	0	(5,172)	4,126	0	0	1,046
Distribution to MPC for acquisitions	(4,100)	0	0	0	(936)	(3,164)	0	0	0
Noncontrolling interests	(2,058)	0	(722)	0	(1,097)	0	0	0	(239)
(Placeholder)	(17)	0	0	0	0	0	0	(17)	0
Contributions from noncontrolling interests	11	0	0	0	0	0	0	11	0
Unit conversion	0	0	0	0	(7,926)	7,926	0	0	0
Ending balance at Dec. 31, 2018	17,731	0	8,336	0	(1,612)	0	(16)	156	10,867
Distributions to MPC from Predecessor	0
Contribution from MPC	(346)	0	0	0	(315)	0	0	0	(31)
Stockholders' Equity, Other	13	0	12	0	0	0	1	0	0
Net income (loss)	(1,381)	(17)	(340)	0	(595)	0	0	(28)	(401)
Allocation of MPC's net investment at acquisition	0	(615)	(2,983)	0	(7,199)	0	0	0	10,797
Noncontrolling interests	(2,959)	(21)	(907)	0	(1,529)	0	0	0	(502)
(Placeholder)	(30)	0	0	0	0	0	0	(30)	0
Contributions from noncontrolling interests	95	0	0	0	0	0	0	95	0
Unit conversion	36	0	36	0	0	0	0	0	0
Ending balance at Dec. 31, 2019	$ 16,613	$ 611	$ 10,800	$ 0	$ 4,968	$ 0	$ (15)	$ 249	$ 0