Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	[1]
Statement of Comprehensive Income [Abstract]
Net income/(loss)	$ (2,716)	$ 689	[2],[3],[4]
Other comprehensive income/(loss), net of tax:
Remeasurements of pension and other postretirement benefits related to equity method investments, net of tax	(1)	1
Comprehensive income/(loss)	(2,717)	690
Less comprehensive income attributable to:
Noncontrolling interests	8	6
Comprehensive Income (loss), Net of Tax, Attributable to Predecessor	0	180
Comprehensive income/(loss) attributable to MPLX LP	$ (2,725)	$ 504

[1] Financial information for the first quarter of 2019 has been retrospectively adjusted for the acquisition of ANDX. See Notes 1 and 3.

[2] Financial information for the first quarter of 2019 has been retrospectively adjusted for the acquisition of ANDX. See Notes 1 and 3.

[3] Financial information for the first quarter of 2019 has been retrospectively adjusted for the acquisition of ANDX. See Notes 1 and 3.

[4] Financial information for the first quarter of 2019 has been retrospectively adjusted for the acquisition of ANDX. See Notes 1 and 3.