Consolidated Statements of Income - USD ($) shares in Millions, $ in Millions		3 Months Ended
		Mar. 31, 2022	Mar. 31, 2021
Income from equity method investments		$ 99	$ 70
Other Income		(17)	1
Related Party Transaction, Other Revenues from Transactions with Related Party		27	28
Revenues		2,610	2,339
Related Party Transaction, Purchases from Related Party		319	298
Cost, Depreciation and Amortization	[1]	313	329
Taxes, Miscellaneous		34	32
Costs and Expenses		1,550	1,365
Interest And Other Financial Costs From Related Parties		4	0
Other Nonoperating Income (Expense)		20	27
Interest Expense, Debt, Excluding Amortization		198	198
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent, Total		1,060	974
Provision for income taxes		5	1
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest, Total		838	749
Less: Net income (loss) attributable to noncontrolling interest		8	9
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest, Total		833	748
Limited partners' interest in net income (loss) attributable to MPLX LP		793	708
Net income (loss) attributable to MPLX LP	[2]	825	739
Related Party and Third Party
General and Administrative Expense		78	86
Third Party [Member]
Operating Lease, Lease Income		91	99
Rental cost of sales
Labor and Related Expense		$ 37	$ 32
Limited Partners Common Units [Member]
Net income (loss) attributable to MPLX LP per limited partner unit:
Net Income (Loss), Per Outstanding Limited Partnership Unit, Basic, Net of Tax		$ 0.78	$ 0.68
Common - diluted (in USD per unit)		$ 0.78	$ 0.68
Weighted average limited partner units outstanding:
Common - basic (in shares)		1,015	1,037
Common - diluted (in shares)		1,015	1,037
Service [Member]
Total revenues from contracts with customers		$ 554	$ 589
Revenue from Contract with Customer, Excluding Assessed Tax, Related Parties		915	872
Service, Other [Member]
Total revenues from contracts with customers		123	77
Product [Member]
Total revenues from contracts with customers		497	282
Revenue from Contract with Customer, Excluding Assessed Tax, Related Parties		45	42
Oil and Gas, Refining and Marketing [Member]
Cost of Goods and Services Sold		287	273
Natural Gas, Midstream [Member]
Cost of Goods and Services Sold		467	276
Series A Preferred Stock [Member] | Preferred Partner [Member]
Dividends, Preferred Stock		21	20
Net income (loss) attributable to MPLX LP	[2]	23	20
Series B Preferred Stock [Member] | Preferred Partner [Member]
Dividends, Preferred Stock		11	11
Net income (loss) attributable to MPLX LP	[2]	11	11
Affiliated Entity
Sales-type Lease, Revenue		111	37
Operating Lease, Lease Income, Related Party [Line Items]		165	242
Affiliated Entity | Rental cost of sales - related parties
Labor and Related Expense		15	39
Affiliated Entity | Service [Member]
Revenue from Contract with Customer, Excluding Assessed Tax, Related Parties		915	872
Affiliated Entity | Product [Member]
Revenue from Contract with Customer, Excluding Assessed Tax, Related Parties		$ 45	$ 42

[1] Depreciation and amortization attributable to L&S was $130 million and $147 million for the three months ended March 31, 2022 and March 31, 2021, respectively. Depreciation and amortization attributable to G&P was $183 million and $182 million for the three months ended March 31, 2022 and March 31, 2021, respectively.

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