Consolidated Statements of Income - USD ($) shares in Millions, $ in Millions		12 Months Ended
		Dec. 31, 2019		Dec. 31, 2018	Dec. 31, 2017
Revenues and other income:
Revenue from Contract with Customer, Excluding Assessed Tax		$ 7,041		$ 5,449
Rental income		388		352	$ 277
Rental income - related parties		1,196		846	279
Income from equity method investments	[1],[2]	290		247	78
Other income		12		7	6
Other income - related parties		114		99	92
Total revenues and other income		9,041		7,005	3,867
Costs and expenses:
Rental cost of sales		141		135	62
Rental cost of sales - related parties		165		31	2
Purchases - related parties		1,231		925	455
Depreciation and amortization	[3]	1,254		867	683
Impairment expense		1,197		0	0
General and administrative expenses		388		316	241
Other taxes		113		83	54
Total costs and expenses		6,664		4,277	2,676
Income from operations		2,377		2,728	1,191
Related party interest and other financial costs		11		5	2
Interest expense (net of amounts capitalized of $51 million, $37 million and $32 million, respectively)		851		590	296
Other financial costs		53		119	56
Income before income taxes		1,462		2,014	837
Provision for income taxes		0		8	1
Net income		1,462		2,006	836
Less: Net income attributable to noncontrolling interests		28		16	6
Less: Net income attributable to Predecessor		401		172	36
Net income attributable to MPLX LP	[4]	1,033		1,818	794
Less: Series A preferred unit distributions					65
Less: General partner’s interest in net income attributable to MPLX LP		0		0	318
Limited partners’ interest in net income attributable to MPLX LP		$ 935		$ 1,743	$ 411
Weighted average limited partner units outstanding:
Common - basic (in units)		906	[5]	761	393
Common - diluted (in units)		907	[5]	761	396
Preferred Partner [Member]
Costs and expenses:
Net income attributable to MPLX LP	[4]	$ 81		$ 75	$ 65
Limited Partners Common Units
Costs and expenses:
Net income attributable to MPLX LP	[4]	$ 910		$ 1,743	$ 411
Net income attributable to MPLX LP per limited partner unit:
Common - basic (in USD per unit)		$ 1.00		$ 2.29	$ 1.07
Common - diluted (in USD per unit)		$ 1.00		$ 2.29	$ 1.06
Weighted average limited partner units outstanding:
Common - basic (in units)		906	[5]	761	385
Common - diluted (in units)		907	[5]	761	388
Service [Member]
Revenues and other income:
Revenue from Contract with Customer, Excluding Assessed Tax		$ 2,498		$ 1,856	$ 1,156
Revenue from Contract with Customer, Excluding Assessed Tax, Related Parties		3,455		2,404	1,082
Product [Member]
Revenues and other income:
Revenue from Contract with Customer, Excluding Assessed Tax		806		887	889
Revenue from Contract with Customer, Excluding Assessed Tax, Related Parties	[6]	142		87	8
Oil and Gas, Refining and Marketing [Member]
Costs and expenses:
Cost of Goods and Services Sold		1,489		1,096	528
Natural Gas, Midstream [Member]
Costs and expenses:
Cost of Goods and Services Sold		686		824	651
Service, Other [Member]
Revenues and other income:
Revenue from Contract with Customer, Excluding Assessed Tax		140		220	0
Series A Preferred Stock [Member] | Preferred Partner [Member]
Costs and expenses:
Less: Series A preferred unit distributions		81		75
Series B Preferred Stock [Member] | Preferred Partner [Member]
Costs and expenses:
Less: Series A preferred unit distributions		$ 17		$ 0	$ 0

[1] “Income from equity method investments” includes the impact of any basis differential amortization or accretion.

[2] The financial information for equity method investments for 2019 includes financial information of equity method investments acquired as part of the Merger. The financial information for equity method investments for 2018 includes financial information of equity method investments acquired as part of the Merger for the last three months of 2018. The financial information for equity method investments for 2017 does not include financial information of equity method investments acquired as part of the Merger. See Note 1 for additional information

[3] Depreciation and amortization attributable to L&S was $503 million, $308 million and $163 million for the years ended 2019, 2018 and 2017, respectively. Depreciation and amortization attributable to G&P was $751 million, $559 million and $520 million for 2019, 2018 and 2017, respectively.

[4] Allocation of net income/(loss) attributable to MPLX LP assumes all earnings for the period had been distributed based on the distribution priorities applicable to the period.

[5] The Series B preferred units and the MPLX common units issued in connection with the Merger were not outstanding during the entire year. See Notes 4 and 8 for additional information about the treatment of these units.

[6] There were additional product sales to MPC that net to zero within the consolidated financial statements as the transactions are recorded net due to the terms of the agreements under which such product was sold. For 2019, 2018 and 2017, these sales totaled $1,120 million, $607 million and $254 million, respectively.