Consolidated Statements of Income - USD ($) shares in Millions, $ in Millions		3 Months Ended		6 Months Ended
		Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Income from equity method investments		$ 111	$ 66	$ 210	$ 136
Other Income		6	3	(11)	4
Related Party Transaction, Other Revenues from Transactions with Related Party		27	27	54	55
Revenues		2,940	2,395	5,550	4,734
Purchases - related parties		351	297	670	595
Cost, Depreciation and Amortization	[1]	310	318	623	647
General and Administrative Expense		82	87	160	173
Taxes, Miscellaneous		33	34	67	66
Costs and Expenses		1,823	1,464	3,373	2,829
Interest And Other Financial Costs From Related Parties		1	2	5	2
Other Nonoperating Income (Expense)		20	19	40	46
Interest Expense, Debt, Excluding Amortization		212	195	410	393
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent, Total		1,117	931	2,177	1,905
Provision for income taxes		0	0	5	1
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest, Total		884	715	1,722	1,464
Less: Net income (loss) attributable to noncontrolling interest		9	9	17	18
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest, Total		884	715	1,717	1,463
Limited partners' interest in net income (loss) attributable to MPLX LP		844	675	1,637	1,383
Net income (loss) attributable to MPLX LP	[2]	$ 875	$ 706	$ 1,700	$ 1,445
Net income (loss) attributable to MPLX LP per limited partner unit:
Net Income (Loss), Per Outstanding Limited Partnership Unit, Basic, Net of Tax		$ 0.83	$ 0.66	$ 1.61	$ 1.34
Common - diluted (in USD per unit)		$ 0.83	$ 0.66	$ 1.61	$ 1.34
Weighted average limited partner units outstanding:
Common - basic (in shares)		1,012	1,029	1,013	1,033
Common - diluted (in shares)		1,012	1,029	1,014	1,033
Asset Impairment Charges		$ 0	$ 42	$ 0	$ 42
Third Party [Member]
Operating Lease, Lease Income		102	99	193	198
Direct Costs of Leased and Rented Property or Equipment		42	32	79	64
Service [Member] | Third Party [Member]
Total revenues from contracts with customers		577	578	1,131	1,167
Service, Other [Member]
Total revenues from contracts with customers		118	76	241	153
Product [Member] | Third Party [Member]
Total revenues from contracts with customers		698	304	1,195	586
Oil and Gas, Refining and Marketing [Member]
Cost of Goods and Services Sold		323	293	610	566
Natural Gas, Midstream [Member]
Cost of Goods and Services Sold		663	338	1,130	614
Series A Preferred Stock [Member] | Preferred Partner [Member]
Dividends, Preferred Stock		21	21	42	41
Net income (loss) attributable to MPLX LP	[2]	25	21	48	41
Series B Preferred Stock [Member] | Preferred Partner [Member]
Dividends, Preferred Stock		10	10	21	21
Net income (loss) attributable to MPLX LP	[2]	10	10	21	21
Affiliated Entity
Sales-type Lease, Revenue		114	136	225	173
Operating Lease, Lease Income, Related Party		198	168	363	410
Direct costs of leased and rented property or equipment, related parties		19	23	34	62
Affiliated Entity | Service [Member]
Total revenues from contracts with customers		938	907	1,853	1,779
Affiliated Entity | Product [Member]
Total revenues from contracts with customers		$ 51	$ 31	$ 96	$ 73

[1] Depreciation and amortization attributable to L&S was $129 million and $259 million for the three and six months ended June 30, 2022, respectively, and $136 million and $283 million for the three and six months ended June 30, 2021, respectively. Depreciation and amortization attributable to G&P was $181 million and $364 million for the three and six months ended June 30, 2022, respectively, and $182 million and $364 million for the three and six months ended June 30, 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.