Consolidated Statements of Income - USD ($) shares in Millions, $ in Millions		3 Months Ended			9 Months Ended
		Sep. 30, 2022		Sep. 30, 2021	Sep. 30, 2022		Sep. 30, 2021
Sales-type Lease, Revenue		$ 28		$ 0	$ 28		$ 0
Sales-type lease revenue, related parties		118		132	343		305
Operating Lease, Lease Income		75		88	268		286
Operating Lease, Lease Income, Related Party		201		164	564		574
Income from equity method investments		125		92	335		228
Other Income		505	[1]	(2)	494	[1]	2
Related Party Transaction, Other Revenues from Transactions with Related Party		28		27	82		82
Revenues		3,401		2,559	8,951		7,293
Costs and Expenses, Related Party		364		307	1,034		902
Cost, Depreciation and Amortization	[2]	302		324	925		971
Asset Impairment Charges		0		0	0		42
General and Administrative Expense		88		94	248		267
Taxes, Miscellaneous		30		27	97		93
Costs and Expenses		1,727		1,528	5,100		4,357
Interest And Other Financial Costs From Related Parties		0		2	5		4
Other Nonoperating Income (Expense)		19		21	59		67
Interest Expense, Debt, Excluding Amortization		217		197	627		590
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent, Total		1,674		1,031	3,851		2,936
Provision for income taxes		1		0	6		1
Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest, Total		1,438		811	3,160		2,275
Less: Net income (loss) attributable to noncontrolling interest		9		9	26		27
Net Income (Loss), Including Portion Attributable to Noncontrolling Interest, Total		1,437		811	3,154		2,274
Limited partners' interest in net income (loss) attributable to MPLX LP		1,395		754	3,032		2,137
Net income (loss) attributable to MPLX LP	[3]	$ 1,428	[4]	$ 802	$ 3,128	[4]	$ 2,247
Net income (loss) attributable to MPLX LP per limited partner unit:
Net Income (Loss), Per Outstanding Limited Partnership Unit, Basic, Net of Tax		$ 1.36		$ 0.74	$ 2.97		$ 2.07
Common - diluted (in USD per unit)		$ 1.36		$ 0.74	$ 2.97		$ 2.07
Weighted average limited partner units outstanding:
Common - basic (in shares)		1,010		1,024	1,012		1,030
Common - diluted (in shares)		1,011		1,025	1,013		1,030
Third Party [Member]
Direct Costs of Leased and Rented Property or Equipment		$ 22		$ 33	$ 101		$ 97
Service [Member]
Total revenues from contracts with customers		627		600	1,758		1,767
Revenue from Contract with Customer, Excluding Assessed Tax, Related Parties		948		902	2,801		2,681
Service [Member] | Third Party [Member]
Total revenues from contracts with customers		627		600	1,758		1,767
Service, Other [Member]
Total revenues from contracts with customers		83		82	324		235
Product [Member]
Total revenues from contracts with customers		617		448	1,812		1,034
Revenue from Contract with Customer, Excluding Assessed Tax, Related Parties		46		26	142		99
Product [Member] | Third Party [Member]
Total revenues from contracts with customers		617		448	1,812		1,034
Oil and Gas, Refining and Marketing [Member]
Cost of Goods and Services Sold		371		298	981		864
Natural Gas, Midstream [Member]
Cost of Goods and Services Sold		540		421	1,670		1,035
Series A Preferred Stock [Member]
Dividends, Preferred Stock		23		38	65		79
Series A Preferred Stock [Member] | Preferred Partner [Member]
Net income (loss) attributable to MPLX LP	[3]	41	[4]	38	89	[4]	79
Series B Preferred Stock [Member]
Dividends, Preferred Stock		10		10	31		31
Series B Preferred Stock [Member] | Preferred Partner [Member]
Net income (loss) attributable to MPLX LP	[3]	10	[4]	10	31	[4]	31
Affiliated Entity
Direct costs of leased and rented property or equipment, related parties		$ 10		$ 24	$ 44		$ 86

[1] The three and nine months ended September 30, 2022 include a $509 million non-cash gain on a lease reclassification. See Note 14 for additional information.

[2] Depreciation and amortization attributable to L&S was $128 million and $387 million for the three and nine months ended September 30, 2022, respectively, and $131 million and $414 million for the three and nine months ended September 30, 2021, respectively. Depreciation and amortization attributable to G&P was $174 million and $538 million for the three and nine months ended September 30, 2022, respectively, and $193 million and $557 million for the three and nine months ended September 30, 2021, respectively. (2)    Includes unrealized derivative gain/ (loss), non-cash equity-based compensation, and other miscellaneous items.

[3] 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.

[4] The three and nine months ended September 30, 2022 include a $509 million non-cash gain on a lease reclassification. See Note 14 for additional information.