MPLX (MPLX) 10-Q 30 Apr 24 2024 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2024	Apr. 26, 2024
Cover [Abstract]
Entity Central Index Key	0001552000
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2024
Document Fiscal Period Focus	Q1
Amendment Flag	false
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Mar. 31, 2024
Document Transition Report	false
Entity File Number	001-35714
Entity Registrant Name	MPLX LP
Entity Incorporation, State or Country Code	DE
Entity Tax Identification Number	27-0005456
Entity Address, Address Line One	200 E. Hardin Street,
Entity Address, City or Town	Findlay,
Entity Address, State or Province	OH
Entity Address, Postal Zip Code	45840
City Area Code	419
Local Phone Number	422-2121
Title of 12(b) Security	Common Units Representing Limited Partnership Interests
Trading Symbol	MPLX
Security Exchange Name	NYSE
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Shell Company	false
Entity Partnership, Units Outstanding		1,016,195,695

Consolidated Statements of Inco

Consolidated Statements of Income - USD ($) shares in Millions, $ in Millions		3 Months Ended
		Mar. 31, 2024	Mar. 31, 2023
Sales-type lease revenue		$ 34	$ 34
Sales-type lease revenue - related parties		121	125
Income from equity method investments		157	134
Total revenues and other income		2,846	2,713
Costs and Expenses, Related Party		372	361
Depreciation and amortization	[1]	317	296
General and administrative expenses		109	89
Other taxes		34	30
Total costs and expenses		1,595	1,517
Income from operations		1,251	1,196
Net interest and other financial costs		235	243
Income before income taxes		1,016	953
Provision for income taxes		1	1
Net income		1,015	952
Less: Net income attributable to noncontrolling interests		10	9
Net income attributable to MPLX LP	[2]	1,005	943
Limited partners' interest in net income attributable to MPLX LP		$ 995	$ 915
Net income attributable to MPLX LP per limited partner unit:
Common - basic		$ 0.98	$ 0.91
Common - diluted		$ 0.98	$ 0.91
Weighted average limited partner units outstanding:
Common - basic		1,008	1,001
Common - diluted		1,008	1,001
Nonrelated Party [Member]
Rental income		$ 60	$ 61
Other Income		45	3
Rental cost of sales		19	20
Related Party [Member]
Rental income		217	202
Other Income		40	27
Rental cost of sales		4	7
General and administrative expenses		73	64
Service [Member]
Revenue from Contract with Customer, Excluding Assessed Tax - third and related parties		658	605
Revenue from Contract with Customer, Excluding Assessed Tax, Related Parties		986	953
Service, Other [Member]
Revenue from Contract with Customer, Excluding Assessed Tax - third and related parties		95	79
Product [Member]
Revenue from Contract with Customer, Excluding Assessed Tax - third and related parties		370	420
Revenue from Contract with Customer, Excluding Assessed Tax, Related Parties		63	70
Oil and Gas, Refining and Marketing [Member]
Cost of Goods and Services Sold		371	308
Natural Gas, Midstream [Member]
Cost of Goods and Services Sold		369	406
Series A Preferred Stock [Member]
Dividends, Preferred Stock		10	23
Series B Preferred Stock [Member]
Dividends, Preferred Stock		$ 0	$ 5
[1]Depreciation and amortization attributable to L&S was $130 million and $129 million for the three months ended March 31, 2024 and March 31, 2023, respectively. Depreciation and amortization attributable to G&P was $187 million and $167 million for the three months ended March 31, 2024 and March 31, 2023, respectively.[2]Allocation of net income attributable to MPLX LP assumes all earnings for the period have been distributed based on the distribution priorities applicable to the period.

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Net income	$ 1,015	$ 952
Other Comprehensive Income (Loss), Net of Tax	1	4
Comprehensive income	1,016	956
Less comprehensive income attributable to:
Noncontrolling interests	10	9
Comprehensive income attributable to MPLX LP	$ 1,006	$ 947

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023
Assets
Cash and cash equivalents	$ 385	$ 1,048
Receivables, net	752	823
Inventories	163	159
Other current assets	36	30
Total current assets	2,139	2,808
Equity method investments	4,343	3,743
Property, plant and equipment, net	19,299	19,264
Intangibles, net	618	654
Goodwill	7,645	7,645
Right of use assets, net	290	264
Other noncurrent assets	976	990
Total assets	36,461	36,529
Liabilities
Accounts payable	132	153
Accrued liabilities	248	300
Accrued property, plant and equipment	166	216
Long-term debt due within one year	1,639	1,135
Accrued interest payable	187	242
Operating lease liabilities	50	45
Total current liabilities	2,960	2,624
Long-term deferred revenue	349	347
Long-term debt	18,805	19,296
Deferred income taxes	16	16
Long-term operating lease liabilities	231	211
Other long-term liabilities	133	126
Total liabilities	22,814	22,945
Commitments and contingencies (see Note 16)
Temporary Equity, Carrying Amount, Attributable to Parent	561	895
Equity
Accumulated other comprehensive loss	(3)	(4)
Total MPLX LP partners’ capital	12,852	12,454
Noncontrolling interests	234	235
Total equity	13,086	12,689
Total liabilities, preferred units and equity	36,461	36,529
Related Party [Member]
Assets
Receivables, net	610	587
Current assets - related parties	803	748
Other current assets	8	7
Right of use assets, net	227	227
Noncurrent assets - related parties	1,151	1,161
Liabilities
Operating lease liabilities	1	1
Other current liabilities	351	360
Long-term deferred revenue	95	99
Long-term liabilities - related parties	320	325
Equity
Limited Partners' Capital Account	3,858	3,758
Nonrelated Party [Member]
Liabilities
Other current liabilities	187	173
Long-term deferred revenue	346	344
Equity
Limited Partners' Capital Account	$ 8,997	$ 8,700

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - shares	Mar. 31, 2024	Dec. 31, 2023
Units Outstanding	1,011,786,074	1,003,498,875
Series A Preferred Stock [Member]
Preferred Units, Outstanding	17,000,000	27,000,000
Common Unit-holders Public | Nonrelated Party [Member]
Units Outstanding	364,000,000	356,000,000
Common Unit-holders Public | Related Party [Member]
Units Outstanding	647,000,000	647,000,000

Consolidated Statements of Cash

Consolidated Statements of Cash Flows - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2024		Mar. 31, 2023
Operating activities:
Net income		$ 1,015		$ 952
Adjustments to reconcile net income to net cash provided by operating activities:
Amortization of deferred financing costs		13		17
Depreciation and amortization	[1]	317		296
Gain on sales-type leases and equity method investments		(20)		0
Income from equity method investments		(157)		(134)
Distributions from unconsolidated affiliates		180		140
Change in fair value of derivatives		8		(5)
Changes in:
Receivables		95		38
Inventories		(4)		(2)
Accounts payable and accrued liabilities		(115)		(130)
Assets/liabilities - related parties		(46)		44
Right of use assets/operating lease liabilities		(1)		(1)
Deferred revenue		9		3
All other, net		(3)		9
Net cash provided by operating activities		1,291		1,227
Net Cash Provided by (Used in) Investing Activities [Abstract]
Additions to property, plant and equipment		(255)		(169)
Payments to Acquire Businesses, Net of Cash Acquired		622		0
Investments in unconsolidated affiliates		(119)		(51)
Net cash used in investing activities		(996)		(220)
Net Cash Provided by (Used in) Financing Activities [Abstract]
Long-term debt borrowings		0		1,589
Long-term debt - repayments		0		(1,000)
Debt issuance costs		0		15
Unit repurchases		(75)	[2]	0
Distributions to noncontrolling interests		(11)		(10)
Distributions to unitholders and general partner		(853)		(777)
Contributions from MPC		10		8
All other, net		(6)		(3)
Net cash used in financing activities		(958)		(852)
Net change in cash, cash equivalents and restricted cash		(663)		155
Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents, Beginning Balance		1,048		238
Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents, Ending Balance		385		393
Series A Preferred Stock [Member]
Net Cash Provided by (Used in) Financing Activities [Abstract]
Distributions to preferred unitholders		(23)		(23)
Series B Preferred Stock [Member]
Net Cash Provided by (Used in) Financing Activities [Abstract]
Redemption of Series B preferred units		0		(600)
Distributions to preferred unitholders		$ 0		$ (21)
[1]Depreciation and amortization attributable to L&S was $130 million and $129 million for the three months ended March 31, 2024 and March 31, 2023, respectively. Depreciation and amortization attributable to G&P was $187 million and $167 million for the three months ended March 31, 2024 and March 31, 2023, respectively.[2]Cash paid for common units repurchased and average cost per unit includes commissions paid to brokers during the period.

Consolidated Statements of Equi

Consolidated Statements of Equity and Series A Preferred Units (Consolidated Statements of Equity) - USD ($) $ in Millions	Total	Common Unit-holders Public	Common Unit-holder MPC	Accumulated Other Comprehensive Loss	Non-controlling Interests	Series B Preferred Unit-holders
Beginning Balance at Dec. 31, 2022	$ 12,546	$ 8,413	$ 3,293	$ (8)	$ 237	$ 611
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	929	323	592	0	9	5
Partners' Capital Account, Redemptions	(600)	(2)	(3)	0	0	(595)
Distributions	(808)	(275)	(502)	0		(21)
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders					(10)
Contributions	8	0	8	0	0	0
Other	5	0	0	4	1	0
Ending Balance at Mar. 31, 2023	12,080	8,459	3,388	(4)	237	$ 0
Beginning Balance at Dec. 31, 2023	12,689	8,700	3,758	(4)	235
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Net income	1,005	355	640	0	10
Unit repurchases	(75)	(75)	0	0	0
Partners' Capital Account, Exchanges and Conversions	321	321	0	0	0
Distributions	(864)	(303)	(550)	0
Noncontrolling Interest, Decrease from Distributions to Noncontrolling Interest Holders					(11)
Contributions	10	0	10	0	0
Other	0	(1)	0	1	0
Ending Balance at Mar. 31, 2024	$ 13,086	$ 8,997	$ 3,858	$ (3)	$ 234

Consolidated Statements of Eq_2

Consolidated Statements of Equity and Series A Preferred Units (Temporary Equity) - USD ($) $ in Millions	Total	Series A Preferred Unit-holders
Beginning Balance at Dec. 31, 2022		$ 968
Temporary Equity, Net Income		23
Temporary Equity Account, Distributions		23
Ending Balance at Mar. 31, 2023		968
Beginning Balance at Dec. 31, 2023	$ 895	895
Temporary Equity, Net Income		10
Preferred unit conversions		(321)
Temporary Equity Account, Distributions		23
Ending Balance at Mar. 31, 2024	$ 561	$ 561

Description of the Business and

Description of the Business and Basis of Presentation	3 Months Ended
	Mar. 31, 2024
Accounting Policies [Abstract]
Business Description and Basis of Presentation	Description of the Business and Basis of Presentation Description of the Business MPLX LP is a diversified, large-cap master limited partnership formed by Marathon Petroleum Corporation that owns and operates midstream energy infrastructure and logistics assets, and provides fuels distribution services. We are engaged in the gathering, transportation, storage and distribution of crude oil, refined products, other hydrocarbon-based products and renewables; the gathering, processing and transportation of natural gas; and the transportation, fractionation, storage and marketing of NGLs. MPLX’s principal executive office is located in Findlay, Ohio. MPLX was formed on March 27, 2012 as a Delaware limited partnership and completed its initial public offering on October 31, 2012. MPLX’s business consists of two segments based on the nature of services it offers: Logistics and Storage (“L&S”), which relates primarily to crude oil, refined products, other hydrocarbon-based products and renewables; and Gathering and Processing (“G&P”), which relates primarily to natural gas and NGLs. See Note 8 for additional information regarding the operations and results of these segments. Basis of Presentation These interim consolidated financial statements are unaudited; however, in the opinion of MPLX’s management, these statements reflect all adjustments necessary for a fair statement of the results for the periods reported. All such adjustments are of a normal, recurring nature unless otherwise disclosed. These interim consolidated financial statements, including the notes, have been prepared in accordance with the rules and regulations of the SEC applicable to interim period financial statements and do not include all of the information and disclosures required by GAAP for complete financial statements. Certain information derived from our audited annual financial statements, prepared in accordance with GAAP, has been condensed or omitted from these interim financial statements. These interim consolidated financial statements should be read in conjunction with the audited consolidated financial statements and notes thereto included in our Annual Report on Form 10-K for the year ended December 31, 2023. The results of operations for the three months ended March 31, 2024 are not necessarily indicative of the results to be expected for the full year. MPLX’s consolidated financial statements include all majority-owned and controlled subsidiaries. For non-wholly owned consolidated subsidiaries, the interests owned by third parties have been recorded as Noncontrolling interests on the accompanying Consolidated Balance Sheets. Intercompany accounts and transactions have been eliminated. MPLX’s investments in which MPLX exercises significant influence but does not control and does not have a controlling financial interest are accounted for using the equity method. MPLX’s investments in VIEs in which MPLX exercises significant influence but does not control and is not the primary beneficiary are also accounted for using the equity method. Certain prior period financial statement amounts have been reclassified to conform to current period presentation.

Accounting Standards

Accounting Standards	3 Months Ended
	Mar. 31, 2024
Accounting Standards Update and Change in Accounting Principle [Abstract]
Accounting Standards	Accounting Standards and Disclosure Rules Recently Adopted During the first quarter of 2024, we adopted ASU 2023-01, Leases (Topic 842): Common Control Arrangements . The adoption of this ASU did not have a material impact on our financial statements or disclosures. Not Yet Adopted SEC Release No. 33-11275, The Enhancement and Standardization of Climate-Related Disclosures for Investors In March 2024, the SEC adopted rules under SEC Release No. 33-11275, The Enhancement and Standardization of Climate-Related Disclosures for Investors, which requires registrants to provide certain climate-related information in their annual reports. As part of the disclosures, material impacts from severe weather events and other natural conditions will be required in the audited financial statements. In April 2024, the SEC voluntarily stayed the rules pending judicial review. Pending the results of the judicial review, the disclosure requirements are effective for the Partnership’s Annual Report on Form 10-K for the fiscal year ended December 31, 2025. We are evaluating the impact these rules will have on our disclosures and monitoring the status of the judicial review. ASU 2023-07, Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures In November 2023, the FASB issued an ASU to update reportable segment disclosure requirements primarily by requiring enhanced disclosures about significant segment expenses. This ASU is effective for fiscal years beginning after December 15, 2023, and for interim periods within fiscal years beginning after December 15, 2024. Early adoption is permitted. The amendments should be applied retrospectively to all prior periods presented in the financial statements. We are currently evaluating the impact this ASU will have on our disclosures.

Business Combinations and Asset

Business Combinations and Asset Acquisitions	3 Months Ended
	Mar. 31, 2024
Business Combination and Asset Acquisition [Abstract]
Business Combination Disclosure [Text Block]	Acquisition Utica Midstream Acquisition On March 22, 2024, MPLX used $625 million of cash on hand to purchase additional ownership interest in existing joint ventures and gathering assets (“Utica Midstream Acquisition”), which will enhance our position in the Utica basin. Prior to the acquisition, we owned an indirect interest in Ohio Gathering Company L.L.C. (“OGC”) and a direct interest in Ohio Condensate Company L.L.C. (“OCC”) and now own a combined 73 percent interest in OGC, a 100 percent interest in OCC, and a 100 percent interest in a dry gas gathering system in the Utica basin, including 53 miles of gathering pipeline and three dehydration units with a combined capacity of approximately 620 MMcf/d. OGC continues to be accounted for as an equity method investment, as MPLX did not obtain control of OGC as a result of the transaction. The acquisition date fair value of our investment in OGC exceeded our portion of the underlying net assets of the joint venture by approximately $86 million. OCC was previously accounted for as an equity method investment, and it is now reflected as a consolidated subsidiary within our consolidated financial results. The results for the acquired business are reported within our G&P segment. The acquisition was accounted for as a business combination requiring all the acquired assets and liabilities to be remeasured to fair value resulting in a consolidated fair value of net assets and liabilities of $625 million. The preliminary determination of the fair value includes $518 million related to acquired interests in the joint ventures and the remaining balance related to other acquired assets and liabilities. The revaluation of MPLX’s existing 62 percent equity method investment in OCC resulted in a $20 million gain, which is included in Other income within the accompanying consolidated statements of income. The fair value of equity method investments was based on a discounted cash flow model.

Related Party Agreements and Tr

Related Party Agreements and Transactions	3 Months Ended
	Mar. 31, 2024
Related Party Transactions [Abstract]
Related Party Agreements and Transactions	Related Party Agreements and Transactions MPLX engages in transactions with both MPC and certain of its equity method investments as part of its normal business; however, transactions with MPC make up the majority of MPLX’s related party transactions. Transactions with related parties are further described below. MPLX has various long-term, fee-based commercial agreements with MPC. Under these agreements, MPLX provides transportation, gathering, terminal, fuels distribution, marketing, storage, management, operational and other services to MPC. MPC has committed to provide MPLX with minimum quarterly throughput volumes on crude oil and refined products and other fees for storage capacity; operating and management fees; and reimbursements for certain direct and indirect costs. MPC has also committed to provide a fixed fee for 100 percent of available capacity for boats, barges and third-party chartered equipment under the marine transportation service agreements. MPLX also has a keep-whole commodity agreement with MPC under which MPC pays us a processing fee for NGLs related to keep-whole agreements and we pay MPC a marketing fee in exchange for assuming the commodity risk. In addition, MPLX has obligations to MPC for services provided to MPLX by MPC under omnibus and employee services type agreements as well as various other agreements. Related Party Loan MPLX is party to a loan agreement (the “MPC Loan Agreement”) with MPC. Under the terms of the MPC Loan Agreement, MPC extends loans to MPLX on a revolving basis as requested by MPLX and as agreed to by MPC. The borrowing capacity of the MPC Loan Agreement is $1.5 billion aggregate principal amount of all loans outstanding at any one time. The MPC Loan Agreement is scheduled to expire, and borrowings under the loan agreement are scheduled to mature and become due and payable, on July 31, 2024, provided that MPC may demand payment of all or any portion of the outstanding principal amount of the loan, together with all accrued and unpaid interest and other amounts (if any), at any time prior to maturity. Borrowings under the MPC Loan Agreement bear interest at one-month term SOFR adjusted upward by 0.10 percent plus 1.25 percent or such lower rate as would be applicable to such loans under the MPLX Credit Agreement as discussed in Note 12. There was no activity on the MPC Loan Agreement for the three months ended March 31, 2024. Related Party Revenue Related party sales to MPC primarily consist of crude oil and refined products pipeline services based on tariff or contracted rates; storage, terminal and fuels distribution services based on contracted rates; and marine transportation services. Related party sales to MPC also consist of revenue related to volume deficiency credits. MPLX also has operating agreements with MPC under which it receives a fee for operating MPC’s retained pipeline assets and a fixed annual fee for providing oversight and management services required to run the marine business. MPLX also receives management fee revenue for engineering, construction and administrative services for operating certain of its equity method investments. Amounts earned under these agreements are classified as Other income - related parties in the Consolidated Statements of Income. Certain product sales to MPC and other related parties 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 the three months ended March 31, 2024 and March 31, 2023, these sales totaled $202 million and $198 million, respectively. Related Party Expenses MPC charges MPLX for executive management services and certain general and administrative services provided to MPLX under the terms of our omnibus agreements (“Omnibus charges”) and for certain employee services provided to MPLX under employee services agreements (“ESA charges”). Omnibus charges and ESA charges are classified as Rental cost of sales - related parties, Purchases - related parties, or General and administrative expenses depending on the nature of the asset or activity with which the costs are associated. In addition to these agreements, MPLX purchases products from MPC, makes payments to MPC in its capacity as general contractor to MPLX, and has certain rent and lease agreements with MPC. For the three months ended March 31, 2024 and March 31, 2023, General and administrative expenses incurred from MPC totaled $73 million and $64 million, respectively. Some charges incurred under the omnibus, employee service and co-location agreements are related to engineering and construction services and are associated with assets under construction. These charges are added to Property, plant and equipment, net on the Consolidated Balance Sheets. For the three months ended March 31, 2024 and March 31, 2023, these charges totaled $41 million and $10 million, respectively. Related Party Assets and Liabilities Assets and liabilities with related parties appearing in the Consolidated Balance Sheets are detailed in the table below. This table identifies the various components of related party assets and liabilities, including those associated with leases and deferred revenue on minimum volume commitments. If MPC fails to meet its minimum committed volumes, MPC will pay MPLX a deficiency payment based on the terms of the agreement. The deficiency amounts received under these agreements (excluding payments received under agreements classified as sales-type leases) are recorded as Current liabilities - related parties. In many cases, MPC may then apply the amount of any such deficiency payments as a credit for volumes in excess of its minimum volume commitment in future periods under the terms of the applicable agreements. MPLX recognizes related party revenues for the deficiency payments when credits are used for volumes in excess of minimum quarterly volume commitments, where it is probable the customer will not use the credit in future periods or upon the expiration of the credits. The use or expiration of the credits is a decrease in Current liabilities - related parties. Deficiency payments under agreements that have been classified as sales-type leases are recorded as a reduction against the corresponding lease receivable. In addition, capital projects MPLX undertakes at the request of MPC are reimbursed in cash and recognized as revenue over the remaining term of the applicable agreements or in some cases, as a contribution from MPC. (In millions) March 31, December 31, Current assets - related parties Receivables $ 610 $ 587 Lease receivables 162 149 Prepaid 23 5 Other 8 7 Total 803 748 Noncurrent assets - related parties Long-term lease receivables 769 789 Right of use assets 227 227 Unguaranteed residual asset 139 126 Long-term receivables 16 19 Total 1,151 1,161 Current liabilities - related parties MPC loan agreement and other payables (1) 261 278 Deferred revenue 89 81 Operating lease liabilities 1 1 Total 351 360 Long-term liabilities - related parties Long-term operating lease liabilities 225 226 Long-term deferred revenue 95 99 Total $ 320 $ 325 (1) There were no borrowings outstanding on the MPC Loan Agreement as of March 31, 2024 or December 31, 2023.

Equity

Equity	3 Months Ended
	Mar. 31, 2024
Equity [Abstract]
Equity	Equity The changes in the number of common units during the three months ended March 31, 2024 are summarized below: (In units) Common Units Balance at December 31, 2023 1,003,498,875 Unit-based compensation awards 135,285 Conversion of Series A preferred units 10,024,831 Units redeemed in unit repurchase program (1,872,917) Balance at March 31, 2024 1,011,786,074 Unit Repurchase Program On August 2, 2022, we announced the board authorization for the repurchase of up to $1 billion of MPLX common units held by the public. This unit repurchase authorization has no expiration date. We may utilize various methods to effect the repurchases, which could include open market repurchases, negotiated block transactions, accelerated unit repurchases, tender offers or open market solicitations for units, some of which may be effected through Rule 10b5-1 plans. The timing and amount of future repurchases, if any, will depend upon several factors, including market and business conditions, and such repurchases may be suspended, discontinued or restarted at any time. Total unit repurchases were as follows for the respective periods: Three Months Ended (In millions, except per unit data) 2024 2023 Number of common units repurchased 2 — Cash paid for common units repurchased (1) $ 75 $ — Average cost per unit (1) $ 40.04 $ — (1) Cash paid for common units repurchased and average cost per unit includes commissions paid to brokers during the period. As of March 31, 2024, we had $771 million remaining under the unit repurchase authorization. Series A Redeemable Preferred Unit Conversions During the three months ended March 31, 2024, certain Series A preferred unitholders exercised their rights to convert their Series A preferred units into approximately 10 million common units. Approximately 17 million Series A preferred units remain outstanding as of March 31, 2024. Series A preferred unitholders exercised their rights to convert an additional 5 million Series A preferred units into common units subsequent to March 31, 2024, but prior to the date the financial statements were filed. Redemption of the Series B Preferred Units On February 15, 2023, MPLX exercised its right to redeem all 600,000 outstanding 6.875 percent Fixed-to-Floating Rate Cumulative Redeemable Perpetual Preferred Units (the “Series B preferred units”). MPLX paid unitholders the Series B preferred unit redemption price of $1,000 per unit. MPLX made a final cash distribution of $21 million to Series B preferred unitholders on February 15, 2023, in conjunction with the redemption. Distributions On April 23, 2024, MPLX declared a cash distribution for the first quarter of 2024, totaling $864 million, or $0.850 per common unit. This distribution will be paid on May 13, 2024 to common unitholders of record on May 3, 2024. This rate will also be received by Series A preferred unitholders. Quarterly distributions for 2024 and 2023 are summarized below: (Per common unit) 2024 2023 March 31, $ 0.850 $ 0.775 The allocation of total quarterly cash distributions to common and preferred unitholders is as follows for the three months ended March 31, 2024 and March 31, 2023. Distributions, although earned, are not accrued until declared. MPLX’s distributions are declared subsequent to quarter end; therefore, the following table represents total cash distributions applicable to the period in which the distributions were earned. Three Months Ended (In millions) 2024 2023 Common and preferred unit distributions: Common unitholders, includes common units of general partner $ 864 $ 776 Series A preferred unit distributions 10 23 Series B preferred unit distributions (1) — 5 Total cash distributions declared $ 874 $ 804 (1) The three months ended March 31, 2023 includes the portion of the $21 million distribution paid to the Series B preferred unitholders on February 15, 2023 that was earned during the period prior to redemption.

Net Income Per Limited Partner

Net Income Per Limited Partner Unit	3 Months Ended
	Mar. 31, 2024
Earnings Per Share [Abstract]
Net Income Per Limited Partner Unit	Net Income Per Limited Partner Unit Net income per unit applicable to common units is computed by dividing net income attributable to MPLX LP less income allocated to participating securities by the weighted average number of common units outstanding. During the three months ended March 31, 2024 and March 31, 2023, MPLX had participating securities consisting of common units, certain equity-based compensation awards, Series A preferred units, and Series B preferred units and also had dilutive potential common units consisting of certain equity-based compensation awards. Potential common units omitted from the diluted earnings per unit calculation for the three months ended March 31, 2024 and March 31, 2023 were less than 1 million. Three Months Ended (In millions, except per unit data) 2024 2023 Net income attributable to MPLX LP (1) : $ 1,005 $ 943 Less: Distributions declared on Series A preferred units 10 23 Distributions declared on Series B preferred units — 5 Undistributed earnings allocated to participating securities 3 4 Impact of redemption of Series B preferred units — 5 Net Income available to common unitholders $ 992 $ 906 Weighted average units outstanding: Basic 1,008 1,001 Diluted 1,008 1,001 Net income attributable to MPLX LP per limited partner unit: Basic $ 0.98 $ 0.91 Diluted $ 0.98 $ 0.91 (1) Allocation of net income attributable to MPLX LP assumes all earnings for the period have been distributed based on the distribution priorities applicable to the period.

Segment Information

Segment Information	3 Months Ended
	Mar. 31, 2024
Segment Reporting [Abstract]
Segment Reporting Disclosure	Segment Information MPLX’s chief operating decision maker (“CODM”) is the chief executive officer of its general partner. The CODM reviews MPLX’s discrete financial information, makes operating decisions, assesses financial performance and allocates resources on a type of service basis. MPLX has two reportable segments: L&S and G&P. Each of these segments is organized and managed based upon the nature of the products and services it offers. • L&S – gathers, transports, stores and distributes crude oil, refined products, other hydrocarbon-based products and renewables. Also includes the operation of refining logistics, fuels distribution and inland marine businesses, terminals, rail facilities, and storage caverns. • G&P – gathers, processes and transports natural gas; and transports, fractionates, stores and markets NGLs. Our CODM evaluates the performance of our segments using Segment Adjusted EBITDA. Amounts included in net income and excluded from Segment Adjusted EBITDA include: (i) depreciation and amortization; (ii) net interest and other financial costs; (iii) income/(loss) from equity method investments; (iv) distributions and adjustments related to equity method investments; (v) impairment expense; (vi) noncontrolling interests; and (vii) other adjustments, as applicable. These items are either: (i) believed to be non-recurring in nature; (ii) not believed to be allocable or controlled by the segment; or (iii) are not tied to the operational performance of the segment. Assets by segment are not a measure used to assess the performance of the Partnership by our CODM and thus are not reported in our disclosures. The tables below present information about revenues and other income, Segment Adjusted EBITDA, capital expenditures and investments in unconsolidated affiliates for our reportable segments: Three Months Ended (In millions) 2024 2023 L&S Service revenue $ 1,067 $ 1,033 Rental income 224 212 Product related revenue 5 5 Sales-type lease revenue 121 125 Income from equity method investments 89 71 Other income 50 14 Total segment revenues and other income (1) 1,556 1,460 Segment Adjusted EBITDA (2) 1,098 1,026 Capital expenditures 84 68 Investments in unconsolidated affiliates (3) 92 15 G&P Service revenue 577 525 Rental income 53 51 Product related revenue 523 564 Sales-type lease revenue 34 34 Income from equity method investments 68 63 Other income 35 16 Total segment revenues and other income (1) 1,290 1,253 Segment Adjusted EBITDA (2) 537 493 Capital expenditures 126 123 Investments in unconsolidated affiliates $ 27 $ 36 (1) Within the total segment revenues and other income amounts presented above, third party revenues for the L&S segment were $207 million and $170 million for the three months ended March 31, 2024 and March 31, 2023, respectively. Third party revenues for the G&P segment were $1,212 million and $1,166 million for the three months ended March 31, 2024 and March 31, 2023, respectively. (2) See below for the reconciliation from Segment Adjusted EBITDA to Net income. (3) The three months ended March 31, 2024 includes a contribution of $92 million to Dakota Access to fund our share of a debt repayment by the joint venture. The table below provides a reconciliation of Segment Adjusted EBITDA for reportable segments to Net income. Three Months Ended (In millions) 2024 2023 Reconciliation to Net income: L&S Segment Adjusted EBITDA $ 1,098 $ 1,026 G&P Segment Adjusted EBITDA 537 493 Total reportable segments 1,635 1,519 Depreciation and amortization (1) (317) (296) Net interest and other financial costs (235) (243) Income from equity method investments 157 134 Distributions/adjustments related to equity method investments (200) (153) Adjusted EBITDA attributable to noncontrolling interests 11 10 Other (2) (36) (19) Net income $ 1,015 $ 952 (1) Depreciation and amortization attributable to L&S was $130 million and $129 million for the three months ended March 31, 2024 and March 31, 2023, respectively. Depreciation and amortization attributable to G&P was $187 million and $167 million for the three months ended March 31, 2024 and March 31, 2023, respectively. (2) Includes unrealized derivative gain/(loss), equity-based compensation, provision for income taxes, and other miscellaneous items.

Property, Plant and Equipment

Property, Plant and Equipment	3 Months Ended
	Mar. 31, 2024
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment	Property, Plant and Equipment Property, plant and equipment with associated accumulated depreciation is shown below: March 31, 2024 December 31, 2023 (In millions) Gross PP&E Accumulated Depreciation Net PP&E Gross PP&E Accumulated Depreciation Net PP&E L&S $ 12,842 $ 4,158 $ 8,684 $ 12,779 $ 4,037 $ 8,742 G&P 14,852 4,237 10,615 14,606 4,084 10,522 Total $ 27,694 $ 8,395 $ 19,299 $ 27,385 $ 8,121 $ 19,264

Fair Value Measurements

Fair Value Measurements	3 Months Ended
	Mar. 31, 2024
Fair Value Disclosures [Abstract]
Fair Value Disclosures	Fair Value Measurements Fair Values – Recurring The following table presents the impact on the Consolidated Balance Sheets of MPLX’s financial instruments carried at fair value on a recurring basis as of March 31, 2024 and December 31, 2023 by fair value hierarchy level. March 31, 2024 December 31, 2023 (In millions) Asset Liability Asset Liability Embedded derivatives in commodity contracts (Level 3) Other current assets / Other current liabilities $ — $ 13 $ — $ 11 Other noncurrent assets / Other long-term liabilities — 56 — 50 Total carrying value in Consolidated Balance Sheets $ — $ 69 $ — $ 61 Level 3 instruments relate to an embedded derivative liability for a natural gas purchase commitment embedded in a keep-whole processing agreement. The fair value calculation for these Level 3 instruments used significant unobservable inputs including: (1) NGL prices interpolated and extrapolated due to inactive markets ranging from $0.66 to $1.61 per gallon with a weighted average of $0.83 per gallon and (2) a 100 percent probability of renewal for the five Changes in Level 3 Fair Value Measurements The following table is a reconciliation of the net beginning and ending balances recorded for net liabilities classified as Level 3 in the fair value hierarchy. Three Months Ended (In millions) 2024 2023 Beginning balance $ (61) $ (61) Unrealized and realized (loss)/gain included in Net Income (1) (12) — Settlements 4 3 Ending balance $ (69) $ (58) The amount of total loss for the period included in earnings attributable to the change in unrealized gain/(loss) relating to liabilities still held at end of period $ (11) $ — (1) (Loss)/gain on derivatives embedded in commodity contracts are recorded in Purchased product costs in the Consolidated Statements of Income. Fair Values – Non-recurring Non-recurring fair value measurements and disclosures in 2024 relate to the purchase of additional ownership interest in existing joint ventures and gathering assets as discussed in Note 3. Fair Values – Reported We believe the carrying value of our other financial instruments, including cash and cash equivalents, receivables, receivables from related parties, lease receivables, lease receivables from related parties, accounts payable, and payables to related parties, approximate fair value. MPLX’s fair value assessment incorporates a variety of considerations, including the duration of the instruments, MPC’s investment-grade credit rating, and the historical incurrence of and expected future insignificance of bad debt expense, which includes an evaluation of counterparty credit risk. The recorded value of the amounts outstanding under the bank revolving credit facility, if any, approximates fair value due to the variable interest rate that approximates current market rates. Derivative instruments are recorded at fair value, based on available market information (see Note 11). The fair value of MPLX’s debt is estimated based on prices from recent trade activity and is categorized in Level 3 of the fair value hierarchy. The following table summarizes the fair value and carrying value of our third-party debt, excluding finance leases and unamortized debt issuance costs: March 31, 2024 December 31, 2023 (In millions) Fair Value Carrying Value Fair Value Carrying Value Outstanding debt (1) $ 19,206 $ 20,557 $ 19,377 $ 20,547 (1) Any amounts outstanding under the MPC Loan Agreement are not included in the table above, as the carrying value approximates fair value. This balance is reflected in Current liabilities - related parties in the Consolidated Balance Sheets.
Fair Value Measurement and Measurement Inputs, Recurring and Nonrecurring	Level 3 instruments relate to an embedded derivative liability for a natural gas purchase commitment embedded in a keep-whole processing agreement. The fair value calculation for these Level 3 instruments used significant unobservable inputs including: (1) NGL prices interpolated and extrapolated due to inactive markets ranging from $0.66 to $1.61 per gallon with a weighted average of $0.83 per gallon and (2) a 100 percent probability of renewal for the five

Derivative Financial Instrument

Derivative Financial Instruments	3 Months Ended
	Mar. 31, 2024
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Disclosure	Derivatives Embedded Derivative - MPLX has a natural gas purchase commitment embedded in a keep-whole processing agreement with a producer customer in the Southern Appalachia region expiring in December 2027. The customer has the unilateral option to extend the agreement for one five Certain derivative positions are subject to master netting agreements; therefore, MPLX has elected to offset derivative assets and liabilities that are legally permissible to be offset. As of March 31, 2024 and December 31, 2023, there were no derivative assets or liabilities that were offset in the Consolidated Balance Sheets. We make a distinction between realized or unrealized gains and losses on derivatives. During the period when a derivative contract is outstanding, changes in the fair value of the derivative are recorded as an unrealized gain or loss. When a derivative contract matures or is settled, the previously recorded unrealized gain or loss is reversed, and the realized gain or loss of the contract is recorded. The impact of MPLX’s derivative contracts not designated as hedging instruments and the location of gains and losses recognized in the Consolidated Statements of Income is summarized below: Three Months Ended (In millions) 2024 2023 Product sales: Unrealized gain $ — $ 2 Product sales derivative gain — 2 Purchased product costs: Realized loss (4) (3) Unrealized (loss)/gain (8) 3 Purchased product cost derivative loss (12) — Total derivative (loss)/gain included in Net income $ (12) $ 2

Debt

Debt	3 Months Ended
	Mar. 31, 2024
Debt Disclosure [Abstract]
Debt	Debt MPLX’s outstanding borrowings consist of the following: (In millions) March 31, December 31, MPLX LP: MPLX Credit Agreement $ — $ — Fixed rate senior notes 20,657 20,657 Consolidated subsidiaries: MarkWest 12 12 ANDX 31 31 Finance lease obligations 6 6 Total 20,706 20,706 Unamortized debt issuance costs (119) (122) Unamortized discount (143) (153) Amounts due within one year (1,639) (1,135) Total long-term debt due after one year $ 18,805 $ 19,296 Credit Agreement MPLX’s credit agreement (the “MPLX Credit Agreement”) matures in July 2027 and, among other things, provides for a $2 billion unsecured revolving credit facility and letter of credit issuing capacity under the facility of up to $150 million. Letter of credit issuing capacity is included in, not in addition to, the $2 billion borrowing capacity. Borrowings under the MPLX Credit Agreement bear interest, at MPLX’s election, at either the Adjusted Term SOFR or the Alternate Base Rate, both as defined in the MPLX Credit Agreement, plus an applicable margin. There was no activity on the MPLX Credit Agreement during the three months ended March 31, 2024. Fixed Rate Senior Notes MPLX’s senior notes, including those issued by consolidated subsidiaries, consist of various series of senior notes maturing between 2024 and 2058 with interest rates ranging from 1.750 percent to 5.650 percent. Interest on each series of notes is payable semi-annually in arrears on various dates depending on the series of the notes.

Interest and Other Financial Co

Interest and Other Financial Costs	3 Months Ended
	Mar. 31, 2024
Other Income and Expenses [Abstract]
Interest and Other Financial Costs	Net Interest and Other Financial Costs Net interest and other financial costs were as follows: Three Months Ended (In millions) 2024 2023 Interest expense $ 228 $ 227 Other financial costs 26 27 Interest income (15) (8) Capitalized interest (4) (3) Net interest and other financial costs $ 235 $ 243

Revenue

Revenue	3 Months Ended
	Mar. 31, 2024
Revenue from Contract with Customer [Abstract]
Revenue	Revenue Disaggregation of Revenue The following tables represent a disaggregation of revenue for each reportable segment for the three months ended March 31, 2024 and March 31, 2023: Three Months Ended March 31, 2024 (In millions) L&S G&P Total Revenues and other income: Service revenue $ 85 $ 573 $ 658 Service revenue - related parties 982 4 986 Service revenue - product related — 95 95 Product sales 2 368 370 Product sales - related parties 3 60 63 Total revenues from contracts with customers $ 1,072 $ 1,100 2,172 Non-ASC 606 revenue (1) 674 Total revenues and other income $ 2,846 Three Months Ended March 31, 2023 (In millions) L&S G&P Total Revenues and other income: Service revenue $ 83 $ 522 $ 605 Service revenue - related parties 950 3 953 Service revenue - product related — 79 79 Product sales 2 418 420 Product sales - related parties 3 67 70 Total revenues from contracts with customers $ 1,038 $ 1,089 2,127 Non-ASC 606 revenue (1) 586 Total revenues and other income $ 2,713 (1) Non-ASC 606 Revenue includes rental income, sales-type lease revenue, income from equity method investments, and other income. Contract Balances Our receivables are primarily associated with customer contracts. Payment terms vary by product or service type; however, the period between invoicing and payment is not significant. Included within the receivables are balances related to commodity sales on behalf of our producer customers, for which we remit the net sales price back to the producer customers upon completion of the sale. Under certain of our contracts, we recognize revenues in excess of billings which we present as contract assets. Contract assets typically relate to deficiency payments related to minimum volume commitments and aid in construction agreements where the revenue recognized and MPLX’s rights to consideration for work completed exceeds the amount billed to the customer. Contract assets are included in Other current assets and Other noncurrent assets on the Consolidated Balance Sheets. Under certain of our contracts, we receive payments in advance of satisfying our performance obligations, which are recorded as contract liabilities. Contract liabilities, which we present as Deferred revenue and Long-term deferred revenue, typically relate to advance payments for aid in construction agreements and deferred customer credits associated with makeup rights and minimum volume commitments. Related to minimum volume commitments, breakage is estimated and recognized into service revenue in instances where it is probable the customer will not use the credit in future periods. We classify contract liabilities as current or long-term based on the timing of when we expect to recognize revenue. The tables below reflect the changes in ASC 606 contract balances for the three months ended March 31, 2024 and March 31, 2023: (In millions) Balance at December 31, 2023 Additions/ (Deletions) Revenue Recognized (1) Balance at March 31, 2024 Contract assets $ 3 $ (1) $ — $ 2 Long-term contract assets 1 — — 1 Deferred revenue 59 19 (12) 66 Deferred revenue - related parties 47 27 (20) 54 Long-term deferred revenue 344 2 — 346 Long-term deferred revenue - related parties $ 29 $ — $ — $ 29 (In millions) Balance at December 31, 2022 Additions/ (Deletions) Revenue Recognized (1) Balance at March 31, 2023 Contract assets $ 21 $ (5) $ — $ 16 Long-term contract assets 1 (1) — — Deferred revenue 57 2 (14) 45 Deferred revenue - related parties 63 32 (26) 69 Long-term deferred revenue 216 15 — 231 Long-term deferred revenue - related parties 25 1 — 26 Contract liabilities — 1 — 1 Long-term contract liabilities $ 2 $ (2) $ — $ — (1) No significant revenue was recognized related to past performance obligations in the current periods. Remaining Performance Obligations The table below includes estimated revenue expected to be recognized in the future related to performance obligations that are unsatisfied (or partially unsatisfied) as of March 31, 2024. The amounts presented below are generally limited to fixed consideration from contracts with customers that contain minimum volume commitments. A significant portion of our future contracted revenue is excluded from the amounts presented below in accordance with ASC 606. Variable consideration that is constrained or not required to be estimated as it reflects our efforts to perform is excluded from this disclosure. Additionally, we do not disclose information on the future performance obligations for any contract with an original expected duration of one year or less, or that are terminable by our customer with little or no termination penalties. Potential future performance obligations related to renewals that have not yet been exercised or are not certain of exercise are excluded from the amounts presented below. Revenues classified as Rental income and Sales-type lease revenue are also excluded from this table. (In billions) 2024 $ 1.5 2025 2.0 2026 1.8 2027 1.7 2028 0.5 2029 and thereafter 0.6 Total estimated revenue on remaining performance obligations $ 8.1 As of March 31, 2024, unsatisfied performance obligations included in the Consolidated Balance Sheets are $495 million and will be recognized as revenue as the obligations are satisfied, which is expected to occur over the next 21 years. A portion of this amount is not disclosed in the table above as it is deemed variable consideration due to volume variability.

Supplemental Cash Flow Informat

Supplemental Cash Flow Information	3 Months Ended
	Mar. 31, 2024
Supplemental Cash Flow Elements [Abstract]
Supplemental Cash Flow Information	Supplemental Cash Flow Information Three Months Ended (In millions) 2024 2023 Net cash provided by operating activities included: Interest paid (net of amounts capitalized) $ 278 $ 270 Income taxes paid — 1 Cash paid for amounts included in the measurement of lease liabilities: Payments on operating leases 19 19 Non-cash investing and financing activities: Net transfers of property, plant and equipment (to)/from materials and supplies inventory (1) 9 Net transfers of property, plant and equipment to lease receivable 25 28 ROU assets obtained in exchange for new operating lease obligations $ 34 $ 2 The Consolidated Statements of Cash Flows exclude changes to the Consolidated Balance Sheets that do not affect cash. The following is a reconciliation of additions to property, plant and equipment to total capital expenditures: Three Months Ended (In millions) 2024 2023 Additions to property, plant and equipment $ 255 $ 169 (Decrease)/Increase in capital accruals (45) 22 Total capital expenditures $ 210 $ 191

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2024
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	Commitments and Contingencies MPLX is the subject of, or a party to, a number of pending or threatened legal actions, contingencies and commitments involving a variety of matters, including laws and regulations relating to the environment. Some of these matters are discussed below. For matters for which MPLX has not recorded a liability, MPLX is unable to estimate a range of possible loss because the issues involved have not been fully developed through pleadings, discovery or court proceedings. However, the ultimate resolution of some of these contingencies could, individually or in the aggregate, be material. Environmental Matters MPLX is subject to federal, state and local laws and regulations relating to the environment. These laws generally provide for control of pollutants released into the environment and require responsible parties to undertake remediation of hazardous waste disposal sites. Penalties may be imposed for non-compliance. Accrued liabilities for remediation totaled $ 17 million 19 million MPLX is involved in environmental enforcement matters arising in the ordinary course of business. While the outcome and impact to MPLX cannot be predicted with certainty, management believes the resolution of these environmental matters will not, individually or collectively, have a material adverse effect on its consolidated results of operations, financial position or cash flows. Other Legal Proceedings In July 2020, Tesoro High Plains Pipeline Company, LLC (“THPP”), a subsidiary of MPLX, received a Notification of Trespass Determination from the Bureau of Indian Affairs (“BIA”) relating to a portion of the Tesoro High Plains Pipeline that crosses the Fort Berthold Reservation in North Dakota. The notification demanded the immediate cessation of pipeline operations and assessed trespass damages of approximately $187 million. After subsequent appeal proceedings and in compliance with a new order issued by the BIA, in December 2020, THPP paid approximately $4 million in assessed trespass damages and ceased use of the portion of the pipeline that crosses the property at issue. In March 2021, the BIA issued an order purporting to vacate the BIA's prior orders related to THPP’s alleged trespass and direct the Regional Director of the BIA to reconsider the issue of THPP’s alleged trespass and issue a new order. In April 2021, THPP filed a lawsuit in the District of North Dakota against the United States of America, the U.S. Department of the Interior and the BIA (collectively, the “U.S. Government Parties”) challenging the March 2021 order purporting to vacate all previous orders related to THPP’s alleged trespass. On February 8, 2022, the U.S. Government Parties filed their answer and counterclaims to THPP’s suit claiming THPP is in continued trespass with respect to the pipeline and seeking disgorgement of pipeline profits from June 1, 2013 to present, removal of the pipeline and remediation. On November 8, 2023, the District Court of North Dakota granted THPP’s motion to sever and stay the U.S. Government Parties’ counterclaims. The case will proceed on the merits of THPP’s challenge to the March 2021 order purporting to vacate all previous orders related to THPP’s alleged trespass. THPP continues not to operate that portion of the pipeline that crosses the property at issue. MPLX is also a party to a number of other lawsuits and other proceedings arising in the ordinary course of business. While the ultimate outcome and impact to MPLX cannot be predicted with certainty, management believes the resolution of these other lawsuits and proceedings will not, individually or collectively, have a material adverse effect on its consolidated financial position, results of operations or cash flows. Guarantees related to indebtedness of equity method investees We hold a 9.19 percent indirect interest in Dakota Access, which owns and operates the Bakken Pipeline system. In 2020, the U.S. District Court for the District of Columbia (the “D.D.C.”) ordered the United States Army Corps of Engineers (“Army Corps”), which granted permits and an easement for the Bakken Pipeline system, to prepare an environmental impact statement (“EIS”) relating to an easement under Lake Oahe in North Dakota. The D.D.C. later vacated the easement. The Army Corps issued a draft EIS in September 2023 detailing various options for the easement going forward, including denying the easement, approving the easement with additional measures, rerouting the easement, or approving the easement with no changes. The Army Corps has not selected a preferred alternative, but will make a decision in its final review, after considering input from the public and other agencies. The pipeline remains operational while the Army Corps finalizes its decision which is expected to be issued by the end of 2024. We have entered into a Contingent Equity Contribution Agreement whereby MPLX LP, along with the other joint venture owners in the Bakken Pipeline system, has agreed to make equity contributions to the joint venture upon certain events occurring to allow the entities that own and operate the Bakken Pipeline system to satisfy their senior note payment obligations. The senior notes were issued to repay amounts owed by the pipeline companies to fund the cost of construction of the Bakken Pipeline system. If the vacatur of the easement results in a temporary shutdown of the pipeline, MPLX would have to contribute its 9.19 percent pro rata share of funds required to pay interest accruing on the notes and any portion of the principal that matures while the pipeline is shutdown. MPLX also expects to contribute its 9.19 percent pro rata share of any costs to remediate any deficiencies to reinstate the easement and/or return the pipeline into operation. If the vacatur of the easement results in a permanent shutdown of the pipeline, MPLX would have to contribute its 9.19 percent pro rata share of the cost to redeem the bonds (including the one percent redemption premium required pursuant to the indenture governing the notes) and any accrued and unpaid interest. As of March 31, 2024, our maximum potential undiscounted payments under the Contingent Equity Contribution Agreement were approximately $170 million. Contractual Commitments and Contingencies From time to time and in the ordinary course of business, MPLX and its affiliates provide guarantees of MPLX’s subsidiaries payment and performance obligations in the G&P segment. Certain natural gas processing and gathering arrangements require MPLX to construct new natural gas processing plants, natural gas gathering pipelines and NGL pipelines and contain certain fees and charges if specified construction milestones are not achieved for reasons other than force majeure. In certain cases, certain producers may have the right to cancel the processing arrangements if there are significant delays that are not due to force majeure. As of March 31, 2024, management does not believe there are any indications that MPLX will not be able to meet the construction milestones, that force majeure does not apply or that such fees and charges will otherwise be triggered.

Insider Trading Arrangements

Insider Trading Arrangements	3 Months Ended
	Mar. 31, 2024
Trading Arrangements, by Individual
Material Terms of Trading Arrangement	During the quarter ended March 31, 2024, no director or officer (as defined in Rule 16a-1(f) promulgated under the Exchange Act) of MPLX adopted or terminated a “Rule 10b5-1 trading arrangement” or “non-Rule 10b5-1 trading arrangement” (as each term is defined in Item 408 of Regulation S-K).
Rule 10b5-1 Arrangement Adopted	false
Non-Rule 10b5-1 Arrangement Adopted	false
Rule 10b5-1 Arrangement Terminated	false
Non-Rule 10b5-1 Arrangement Terminated	false

Description of the Business a_2

Description of the Business and Basis of Presentation Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2024
Accounting Policies [Abstract]
Nature of Operations	We are engaged in the gathering, transportation, storage and distribution of crude oil, refined products, other hydrocarbon-based products and renewables; the gathering, processing and transportation of natural gas; and the transportation, fractionation, storage and marketing of NGLs. MPLX’s principal executive office is located in Findlay, Ohio. MPLX was formed on March 27, 2012 as a Delaware limited partnership and completed its initial public offering on October 31, 2012. MPLX’s business consists of two segments based on the nature of services it offers: Logistics and Storage (“L&S”), which relates primarily to crude oil, refined products, other hydrocarbon-based products and renewables; and Gathering and Processing (“G&P”), which relates primarily to natural gas and NGLs. See Note 8 for additional information regarding the operations and results of these segments.
Basis of Accounting, Policy	These interim consolidated financial statements are unaudited; however, in the opinion of MPLX’s management, these statements reflect all adjustments necessary for a fair statement of the results for the periods reported. All such adjustments are of a normal, recurring nature unless otherwise disclosed. These interim consolidated financial statements, including the notes, have been prepared in accordance with the rules and regulations of the SEC applicable to interim period financial statements and do not include all of the information and disclosures required by GAAP for complete financial statements. Certain information derived from our audited annual financial statements, prepared in accordance with GAAP, has been condensed or omitted from these interim financial statements.
Consolidation, Subsidiaries or Other Investments, Consolidated Entities, Policy	MPLX’s consolidated financial statements include all majority-owned and controlled subsidiaries. For non-wholly owned consolidated subsidiaries, the interests owned by third parties have been recorded as Noncontrolling interests on the accompanying Consolidated Balance Sheets. Intercompany accounts and transactions have been eliminated. MPLX’s investments in which MPLX exercises significant influence but does not control and does not have a controlling financial interest are accounted for using the equity method. MPLX’s investments in VIEs in which MPLX exercises significant influence but does not control and is not the primary beneficiary are also accounted for using the equity method.

Net Income Per Limited Partne_2

Net Income Per Limited Partner Unit Accounting Policy (Policies)	3 Months Ended
	Mar. 31, 2024
Accounting Policies [Abstract]
Earnings Per Unit, Policy	Net income per unit applicable to common units is computed by dividing net income attributable to MPLX LP less income allocated to participating securities by the weighted average number of common units outstanding.

Related Party Agreements and _2

Related Party Agreements and Transactions (Tables)	3 Months Ended
	Mar. 31, 2024
Related Party Transactions [Abstract]
Schedule of Related Party Transactions	Assets and liabilities with related parties appearing in the Consolidated Balance Sheets are detailed in the table below. This table identifies the various components of related party assets and liabilities, including those associated with leases and deferred revenue on minimum volume commitments. If MPC fails to meet its minimum committed volumes, MPC will pay MPLX a deficiency payment based on the terms of the agreement. The deficiency amounts received under these agreements (excluding payments received under agreements classified as sales-type leases) are recorded as Current liabilities - related parties. In many cases, MPC may then apply the amount of any such deficiency payments as a credit for volumes in excess of its minimum volume commitment in future periods under the terms of the applicable agreements. MPLX recognizes related party revenues for the deficiency payments when credits are used for volumes in excess of minimum quarterly volume commitments, where it is probable the customer will not use the credit in future periods or upon the expiration of the credits. The use or expiration of the credits is a decrease in Current liabilities - related parties. Deficiency payments under agreements that have been classified as sales-type leases are recorded as a reduction against the corresponding lease receivable. In addition, capital projects MPLX undertakes at the request of MPC are reimbursed in cash and recognized as revenue over the remaining term of the applicable agreements or in some cases, as a contribution from MPC. (In millions) March 31, December 31, Current assets - related parties Receivables $ 610 $ 587 Lease receivables 162 149 Prepaid 23 5 Other 8 7 Total 803 748 Noncurrent assets - related parties Long-term lease receivables 769 789 Right of use assets 227 227 Unguaranteed residual asset 139 126 Long-term receivables 16 19 Total 1,151 1,161 Current liabilities - related parties MPC loan agreement and other payables (1) 261 278 Deferred revenue 89 81 Operating lease liabilities 1 1 Total 351 360 Long-term liabilities - related parties Long-term operating lease liabilities 225 226 Long-term deferred revenue 95 99 Total $ 320 $ 325 (1) There were no borrowings outstanding on the MPC Loan Agreement as of March 31, 2024 or December 31, 2023.

Equity (Tables)

Equity (Tables)	3 Months Ended
	Mar. 31, 2024
Equity [Abstract]
Schedule of Stockholders Equity	The changes in the number of common units during the three months ended March 31, 2024 are summarized below: (In units) Common Units Balance at December 31, 2023 1,003,498,875 Unit-based compensation awards 135,285 Conversion of Series A preferred units 10,024,831 Units redeemed in unit repurchase program (1,872,917) Balance at March 31, 2024 1,011,786,074
Distributions Made to Limited Partner, by Distribution	The allocation of total quarterly cash distributions to common and preferred unitholders is as follows for the three months ended March 31, 2024 and March 31, 2023. Distributions, although earned, are not accrued until declared. MPLX’s distributions are declared subsequent to quarter end; therefore, the following table represents total cash distributions applicable to the period in which the distributions were earned. Three Months Ended (In millions) 2024 2023 Common and preferred unit distributions: Common unitholders, includes common units of general partner $ 864 $ 776 Series A preferred unit distributions 10 23 Series B preferred unit distributions (1) — 5 Total cash distributions declared $ 874 $ 804 (1) The three months ended March 31, 2023 includes the portion of the $21 million distribution paid to the Series B preferred unitholders on February 15, 2023 that was earned during the period prior to redemption.

Net Income Per Limited Partne_3

Net Income Per Limited Partner Unit (Tables)	3 Months Ended
	Mar. 31, 2024
Earnings Per Share [Abstract]
Schedule of Net Income Per Unit, Basic and Diluted	Three Months Ended (In millions, except per unit data) 2024 2023 Net income attributable to MPLX LP (1) : $ 1,005 $ 943 Less: Distributions declared on Series A preferred units 10 23 Distributions declared on Series B preferred units — 5 Undistributed earnings allocated to participating securities 3 4 Impact of redemption of Series B preferred units — 5 Net Income available to common unitholders $ 992 $ 906 Weighted average units outstanding: Basic 1,008 1,001 Diluted 1,008 1,001 Net income attributable to MPLX LP per limited partner unit: Basic $ 0.98 $ 0.91 Diluted $ 0.98 $ 0.91 (1) Allocation of net income attributable to MPLX LP assumes all earnings for the period have been distributed based on the distribution priorities applicable to the period.

Segment Information (Tables)

Segment Information (Tables)	3 Months Ended
	Mar. 31, 2024
Segment Reporting [Abstract]
Schedule of Segment Reporting Information, by Segment	The tables below present information about revenues and other income, Segment Adjusted EBITDA, capital expenditures and investments in unconsolidated affiliates for our reportable segments: Three Months Ended (In millions) 2024 2023 L&S Service revenue $ 1,067 $ 1,033 Rental income 224 212 Product related revenue 5 5 Sales-type lease revenue 121 125 Income from equity method investments 89 71 Other income 50 14 Total segment revenues and other income (1) 1,556 1,460 Segment Adjusted EBITDA (2) 1,098 1,026 Capital expenditures 84 68 Investments in unconsolidated affiliates (3) 92 15 G&P Service revenue 577 525 Rental income 53 51 Product related revenue 523 564 Sales-type lease revenue 34 34 Income from equity method investments 68 63 Other income 35 16 Total segment revenues and other income (1) 1,290 1,253 Segment Adjusted EBITDA (2) 537 493 Capital expenditures 126 123 Investments in unconsolidated affiliates $ 27 $ 36 (1) Within the total segment revenues and other income amounts presented above, third party revenues for the L&S segment were $207 million and $170 million for the three months ended March 31, 2024 and March 31, 2023, respectively. Third party revenues for the G&P segment were $1,212 million and $1,166 million for the three months ended March 31, 2024 and March 31, 2023, respectively. (2) See below for the reconciliation from Segment Adjusted EBITDA to Net income. (3) The three months ended March 31, 2024 includes a contribution of $92 million to Dakota Access to fund our share of a debt repayment by the joint venture.
Reconciliation of Other Significant Reconciling Items from Segments to Consolidated	The table below provides a reconciliation of Segment Adjusted EBITDA for reportable segments to Net income. Three Months Ended (In millions) 2024 2023 Reconciliation to Net income: L&S Segment Adjusted EBITDA $ 1,098 $ 1,026 G&P Segment Adjusted EBITDA 537 493 Total reportable segments 1,635 1,519 Depreciation and amortization (1) (317) (296) Net interest and other financial costs (235) (243) Income from equity method investments 157 134 Distributions/adjustments related to equity method investments (200) (153) Adjusted EBITDA attributable to noncontrolling interests 11 10 Other (2) (36) (19) Net income $ 1,015 $ 952 (1) Depreciation and amortization attributable to L&S was $130 million and $129 million for the three months ended March 31, 2024 and March 31, 2023, respectively. Depreciation and amortization attributable to G&P was $187 million and $167 million for the three months ended March 31, 2024 and March 31, 2023, respectively. (2) Includes unrealized derivative gain/(loss), equity-based compensation, provision for income taxes, and other miscellaneous items.

Property, Plant and Equipment (

Property, Plant and Equipment (Tables)	3 Months Ended
	Mar. 31, 2024
Property, Plant and Equipment [Abstract]
Summary of Property, Plant and Equipment	Property, plant and equipment with associated accumulated depreciation is shown below: March 31, 2024 December 31, 2023 (In millions) Gross PP&E Accumulated Depreciation Net PP&E Gross PP&E Accumulated Depreciation Net PP&E L&S $ 12,842 $ 4,158 $ 8,684 $ 12,779 $ 4,037 $ 8,742 G&P 14,852 4,237 10,615 14,606 4,084 10,522 Total $ 27,694 $ 8,395 $ 19,299 $ 27,385 $ 8,121 $ 19,264

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	3 Months Ended
	Mar. 31, 2024
Fair Value Disclosures [Abstract]
Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis	The following table presents the impact on the Consolidated Balance Sheets of MPLX’s financial instruments carried at fair value on a recurring basis as of March 31, 2024 and December 31, 2023 by fair value hierarchy level. March 31, 2024 December 31, 2023 (In millions) Asset Liability Asset Liability Embedded derivatives in commodity contracts (Level 3) Other current assets / Other current liabilities $ — $ 13 $ — $ 11 Other noncurrent assets / Other long-term liabilities — 56 — 50 Total carrying value in Consolidated Balance Sheets $ — $ 69 $ — $ 61
Fair Value, Net Derivative Asset (Liability) Measured on Recurring Basis, Unobservable Input Reconciliation	The following table is a reconciliation of the net beginning and ending balances recorded for net liabilities classified as Level 3 in the fair value hierarchy. Three Months Ended (In millions) 2024 2023 Beginning balance $ (61) $ (61) Unrealized and realized (loss)/gain included in Net Income (1) (12) — Settlements 4 3 Ending balance $ (69) $ (58) The amount of total loss for the period included in earnings attributable to the change in unrealized gain/(loss) relating to liabilities still held at end of period $ (11) $ — (1) (Loss)/gain on derivatives embedded in commodity contracts are recorded in Purchased product costs in the Consolidated Statements of Income.
Fair Value Carrying Value by Balance Sheet Grouping	The following table summarizes the fair value and carrying value of our third-party debt, excluding finance leases and unamortized debt issuance costs: March 31, 2024 December 31, 2023 (In millions) Fair Value Carrying Value Fair Value Carrying Value Outstanding debt (1) $ 19,206 $ 20,557 $ 19,377 $ 20,547 (1) Any amounts outstanding under the MPC Loan Agreement are not included in the table above, as the carrying value approximates fair value. This balance is reflected in Current liabilities - related parties in the Consolidated Balance Sheets.

Derivative Financial Instrume_2

Derivative Financial Instruments (Tables)	3 Months Ended
	Mar. 31, 2024
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Schedule of Derivative Instruments, Gain (Loss)	The impact of MPLX’s derivative contracts not designated as hedging instruments and the location of gains and losses recognized in the Consolidated Statements of Income is summarized below: Three Months Ended (In millions) 2024 2023 Product sales: Unrealized gain $ — $ 2 Product sales derivative gain — 2 Purchased product costs: Realized loss (4) (3) Unrealized (loss)/gain (8) 3 Purchased product cost derivative loss (12) — Total derivative (loss)/gain included in Net income $ (12) $ 2

Debt (Tables)

Debt (Tables)	3 Months Ended
	Mar. 31, 2024
Debt Disclosure [Abstract]
Schedule of Debt	MPLX’s outstanding borrowings consist of the following: (In millions) March 31, December 31, MPLX LP: MPLX Credit Agreement $ — $ — Fixed rate senior notes 20,657 20,657 Consolidated subsidiaries: MarkWest 12 12 ANDX 31 31 Finance lease obligations 6 6 Total 20,706 20,706 Unamortized debt issuance costs (119) (122) Unamortized discount (143) (153) Amounts due within one year (1,639) (1,135) Total long-term debt due after one year $ 18,805 $ 19,296

Interest and Other Financial _2

Interest and Other Financial Costs (Tables)	3 Months Ended
	Mar. 31, 2024
Other Income and Expenses [Abstract]
Interest and Other Financial Costs	Net Interest and Other Financial Costs Net interest and other financial costs were as follows: Three Months Ended (In millions) 2024 2023 Interest expense $ 228 $ 227 Other financial costs 26 27 Interest income (15) (8) Capitalized interest (4) (3) Net interest and other financial costs $ 235 $ 243

Revenue (Tables)

Revenue (Tables)	3 Months Ended
	Mar. 31, 2024
Revenue from Contract with Customer [Abstract]
Disaggregation of Revenue Table	The following tables represent a disaggregation of revenue for each reportable segment for the three months ended March 31, 2024 and March 31, 2023: Three Months Ended March 31, 2024 (In millions) L&S G&P Total Revenues and other income: Service revenue $ 85 $ 573 $ 658 Service revenue - related parties 982 4 986 Service revenue - product related — 95 95 Product sales 2 368 370 Product sales - related parties 3 60 63 Total revenues from contracts with customers $ 1,072 $ 1,100 2,172 Non-ASC 606 revenue (1) 674 Total revenues and other income $ 2,846 Three Months Ended March 31, 2023 (In millions) L&S G&P Total Revenues and other income: Service revenue $ 83 $ 522 $ 605 Service revenue - related parties 950 3 953 Service revenue - product related — 79 79 Product sales 2 418 420 Product sales - related parties 3 67 70 Total revenues from contracts with customers $ 1,038 $ 1,089 2,127 Non-ASC 606 revenue (1) 586 Total revenues and other income $ 2,713 (1) Non-ASC 606 Revenue includes rental income, sales-type lease revenue, income from equity method investments, and other income.
Schedule of Contract with Customer, Contract Asset, Contract Liability, and Receivable	The tables below reflect the changes in ASC 606 contract balances for the three months ended March 31, 2024 and March 31, 2023: (In millions) Balance at December 31, 2023 Additions/ (Deletions) Revenue Recognized (1) Balance at March 31, 2024 Contract assets $ 3 $ (1) $ — $ 2 Long-term contract assets 1 — — 1 Deferred revenue 59 19 (12) 66 Deferred revenue - related parties 47 27 (20) 54 Long-term deferred revenue 344 2 — 346 Long-term deferred revenue - related parties $ 29 $ — $ — $ 29 (In millions) Balance at December 31, 2022 Additions/ (Deletions) Revenue Recognized (1) Balance at March 31, 2023 Contract assets $ 21 $ (5) $ — $ 16 Long-term contract assets 1 (1) — — Deferred revenue 57 2 (14) 45 Deferred revenue - related parties 63 32 (26) 69 Long-term deferred revenue 216 15 — 231 Long-term deferred revenue - related parties 25 1 — 26 Contract liabilities — 1 — 1 Long-term contract liabilities $ 2 $ (2) $ — $ — (1) No significant revenue was recognized related to past performance obligations in the current periods.
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction	The table below includes estimated revenue expected to be recognized in the future related to performance obligations that are unsatisfied (or partially unsatisfied) as of March 31, 2024. The amounts presented below are generally limited to fixed consideration from contracts with customers that contain minimum volume commitments. A significant portion of our future contracted revenue is excluded from the amounts presented below in accordance with ASC 606. Variable consideration that is constrained or not required to be estimated as it reflects our efforts to perform is excluded from this disclosure. Additionally, we do not disclose information on the future performance obligations for any contract with an original expected duration of one year or less, or that are terminable by our customer with little or no termination penalties. Potential future performance obligations related to renewals that have not yet been exercised or are not certain of exercise are excluded from the amounts presented below. Revenues classified as Rental income and Sales-type lease revenue are also excluded from this table. (In billions) 2024 $ 1.5 2025 2.0 2026 1.8 2027 1.7 2028 0.5 2029 and thereafter 0.6 Total estimated revenue on remaining performance obligations $ 8.1 As of March 31, 2024, unsatisfied performance obligations included in the Consolidated Balance Sheets are $495 million and will be recognized as revenue as the obligations are satisfied, which is expected to occur over the next 21 years. A portion of this amount is not disclosed in the table above as it is deemed variable consideration due to volume variability.

Supplemental Cash Flow Inform_2

Supplemental Cash Flow Information (Tables)	3 Months Ended
	Mar. 31, 2024
Supplemental Cash Flow Elements [Abstract]
Schedule of Cash Flow, Supplemental Disclosures	Three Months Ended (In millions) 2024 2023 Net cash provided by operating activities included: Interest paid (net of amounts capitalized) $ 278 $ 270 Income taxes paid — 1 Cash paid for amounts included in the measurement of lease liabilities: Payments on operating leases 19 19 Non-cash investing and financing activities: Net transfers of property, plant and equipment (to)/from materials and supplies inventory (1) 9 Net transfers of property, plant and equipment to lease receivable 25 28 ROU assets obtained in exchange for new operating lease obligations $ 34 $ 2
Summary of Reconciliation of Additions to Property, Plant and Equipment to Total Capital Expenditures	The Consolidated Statements of Cash Flows exclude changes to the Consolidated Balance Sheets that do not affect cash. The following is a reconciliation of additions to property, plant and equipment to total capital expenditures: Three Months Ended (In millions) 2024 2023 Additions to property, plant and equipment $ 255 $ 169 (Decrease)/Increase in capital accruals (45) 22 Total capital expenditures $ 210 $ 191

Description of Business and Bas

Description of Business and Basis of Presentation - Additional Information (Detail)	3 Months Ended
	Mar. 31, 2024
Accounting Policies [Abstract]
Number of reportable segments	2

Business Combinations and Ass_2

Business Combinations and Asset Acquisitions (Details) $ in Millions	Mar. 22, 2024 USD ($)
Utica Midstream
Business Acquisition [Line Items]
Business Acquisition, Description of Acquired Entity	On March 22, 2024, MPLX used $625 million of cash on hand to purchase additional ownership interest in existing joint ventures and gathering assets (“Utica Midstream Acquisition”), which will enhance our position in the Utica basin. Prior to the acquisition, we owned an indirect interest in Ohio Gathering Company L.L.C. (“OGC”) and a direct interest in Ohio Condensate Company L.L.C. (“OCC”) and now own a combined 73 percent interest in OGC, a 100 percent interest in OCC, and a 100 percent interest in a dry gas gathering system in the Utica basin, including 53 miles of gathering pipeline and three dehydration units with a combined capacity of approximately 620 MMcf/d.
Payments to Acquire Businesses, Gross	$ 625
Business Acquisition, Percentage of Voting Interests Acquired	100%
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Net	$ 625
Business Combination, Recognized Identifiable Assets Acquired and Liabilities Assumed, Other Noncurrent Assets	$ 518
Ohio Gathering Company L.L.C.
Business Acquisition [Line Items]
Business Combination, Step Acquisition, Equity Interest in Acquiree, Including Subsequent Acquisition, Percentage	73%
Difference between carrying amount and underlying equity	$ 86
Ohio Condensate Company, L.L.C.
Business Acquisition [Line Items]
Business Combination, Step Acquisition, Equity Interest in Acquiree, Remeasurement Gain	$ 20
Business Combination, Step Acquisition, Equity Interest in Acquiree, Including Subsequent Acquisition, Percentage	100%
Business Combination, Step Acquisition, Equity Interest in Acquiree, Percentage	62%

Investments and Noncontrolling

Investments and Noncontrolling Interests (Summary of Equity Method Investment Financial Information) (Details) - USD ($) $ in Millions		Mar. 31, 2024		Dec. 31, 2023
Schedule of Equity Method Investments
Equity method investments		$ 4,343		$ 3,743
L&S
Schedule of Equity Method Investments
Equity method investments		$ 1,925		1,832
L&S | Andeavor Logistics Rio Pipeline LLC
Schedule of Equity Method Investments
Equity method investment, ownership percentage		67%
Equity method investments		$ 168		171
L&S | Illinois Extension Pipeline Company, L.L.C.
Schedule of Equity Method Investments
Equity method investment, ownership percentage		35%
Equity method investments		$ 236		228
L&S | LOOP LLC
Schedule of Equity Method Investments
Equity method investment, ownership percentage		41%
Equity method investments		$ 316		314
L&S | MarEn Bakken Company LLC(1)
Schedule of Equity Method Investments
Equity method investment, ownership percentage		25%
Equity method investments	[1]	$ 535		449
L&S | Minnesota Pipe Line Company, LLC
Schedule of Equity Method Investments
Equity method investment, ownership percentage		17%
Equity method investments		$ 173		174
L&S | Whistler Pipeline LLC
Schedule of Equity Method Investments
Equity method investment, ownership percentage		38%
Equity method investments		$ 206		214
L&S | Other VIEs and Non-VIEs
Schedule of Equity Method Investments
Equity method investments	[2]	$ 291		282
L&S | Indirect Ownership Interest [Member] | Bakken Pipeline System [Member]
Schedule of Equity Method Investments
Equity method investment, ownership percentage		9.19%
G&P
Schedule of Equity Method Investments
Equity method investments		$ 2,418		1,911
G&P | Centrahoma Processing LLC
Schedule of Equity Method Investments
Equity method investment, ownership percentage		40%
Equity method investments		$ 111		114
G&P | MarkWest EMG Jefferson Dry Gas Gathering Company, L.L.C
Schedule of Equity Method Investments
Equity method investment, ownership percentage		67%
Equity method investments		$ 339		336
G&P | MarkWest Utica EMG, L.L.C.
Schedule of Equity Method Investments
Equity method investment, ownership percentage		58%
Equity method investments		$ 692		676
G&P | Ohio Gathering Company L.L.C.
Schedule of Equity Method Investments
Equity method investment, ownership percentage		36%
Equity method investments		$ 503	[3]	0
G&P | Rendezvous Gas Services, L.L.C.
Schedule of Equity Method Investments
Equity method investment, ownership percentage		78%
Equity method investments		$ 127		129
G&P | Sherwood Midstream Holdings LLC
Schedule of Equity Method Investments
Equity method investment, ownership percentage		51%
Equity method investments		$ 110		113
G&P | Sherwood Midstream LLC
Schedule of Equity Method Investments
Equity method investment, ownership percentage		50%
Equity method investments		$ 496		500
G&P | Other VIEs and Non-VIEs
Schedule of Equity Method Investments
Equity method investments		$ 40		$ 43
G&P | Indirect Ownership Interest [Member] | Ohio Gathering Company L.L.C.
Schedule of Equity Method Investments
Equity method investment, ownership percentage		37%
[1]The investment in MarEn Bakken Company LLC includes our 9.19 percent indirect interest in a joint venture (“Dakota Access”) that owns and operates the Dakota Access Pipeline and Energy Transfer Crude Oil Pipeline projects, collectively referred to as the Bakken Pipeline system.[2]Some investments included within Other have also been deemed to be VIEs.[3]We acquired a 36 percent direct interest in OGC in the Utica Midstream Acquisition discussed in Note 3. We also hold a 37 percent indirect interest in OGC through our ownership interest in MarkWest Utica EMG, L.L.C.

Related Party Loan (Details)

Related Party Loan (Details) - Revolving Credit Facility - Related Party [Member] - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Dec. 31, 2023
Related Party Transaction [Line Items]
Line of Credit Facility, Current Borrowing Capacity	$ 1,500
Debt Instrument, Description of Variable Rate Basis	one-month term SOFR adjusted upward by 0.10 percent plus 1.25 percent
Line of Credit, Current	$ 0	$ 0

Related Party Revenue (Details)

Related Party Revenue (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Related Party [Member]
Related Party Transaction [Line Items]
Sales Revenue, Goods, Related Party, Net Zero	$ 202	$ 198

Related Party Expenses (Details

Related Party Expenses (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Related Party Transaction [Line Items]
General and administrative expenses	$ 109	$ 89
Related Party [Member]
Related Party Transaction [Line Items]
General and administrative expenses	73	64
Asset under Construction [Member] | Related Party [Member]
Related Party Transaction [Line Items]
Property, Plant and Equipment, Additions	$ 41	$ 10

Related Party Assest and Liabil

Related Party Assest and Liabilities (Details) - USD ($) $ in Millions		Mar. 31, 2024	Dec. 31, 2023
Related Party Transaction [Line Items]
Receivables		$ 752	$ 823
Other current assets		36	30
Right of use assets		290	264
Operating lease liabilities		50	45
Long-term deferred revenue		349	347
Related Party [Member]
Related Party Transaction [Line Items]
Receivables		610	587
Lease receivables		162	149
Prepaid		23	5
Other current assets		8	7
Current assets - related parties		803	748
Long-term lease receivables		769	789
Right of use assets		227	227
Unguaranteed residual asset		139	126
Long-term receivables		16	19
Noncurrent assets - related parties		1,151	1,161
Accounts payable	[1]	261	278
Deferred revenue		89	81
Operating lease liabilities		1	1
Other current liabilities		351	360
Long-term operating lease liabilities		225	226
Long-term deferred revenue		95	99
Other Liabilities, Noncurrent		320	325
Revolving Credit Facility | Related Party [Member]
Related Party Transaction [Line Items]
Line of Credit, Current		$ 0	$ 0
[1]There were no borrowings outstanding on the MPC Loan Agreement as of March 31, 2024 or December 31, 2023.

Equity - Changes in Partners Ca

Equity - Changes in Partners Capital, Unit Rollforward (Details) - shares	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Stockholders Equity [Line Items]
Balance at December 31, 2023	1,003,498,875
Unit-based compensation awards	135,285
Partners' Capital Account, Units, Converted	10,024,831
Stock Repurchased and Retired During Period, Shares	(1,872,917)	0
Balance at March 31, 2024	1,011,786,074

Equity (Unit Repurchase Program

Equity (Unit Repurchase Program) (Details) - USD ($) $ in Millions	Mar. 31, 2024	Aug. 02, 2022
Equity [Abstract]
Stock Repurchase Program, Remaining Authorized Repurchase Amount	$ 771
Stock Repurchase Program, Authorized Amount		$ 1,000

Equity (Unit Repurchases) (Deta

Equity (Unit Repurchases) (Details) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2024		Mar. 31, 2023
Equity [Abstract]
Number of common units repurchased	1,872,917		0
Cash paid for common units repurchased(1)	$ 75	[1]	$ 0
Average cost per unit(1)	$ 40.04	[1]	$ 0
[1]Cash paid for common units repurchased and average cost per unit includes commissions paid to brokers during the period.

Series A Preferred Units (Detai

Series A Preferred Units (Details) - shares	1 Months Ended	3 Months Ended
	Apr. 29, 2024	Mar. 31, 2024
Preferred Units [Line Items]
Partners' Capital Account, Units, Converted		10,024,831
Series A Preferred Stock [Member]
Preferred Units [Line Items]
Temporary Equity, Shares Outstanding		17,000,000
Subsequent Event
Preferred Units [Line Items]
Partners' Capital Account, Units, Converted	5,000,000

Series B Redemption (Details)

Series B Redemption (Details) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended
	Feb. 15, 2023	Mar. 31, 2024	Mar. 31, 2023
Equity, Class of Treasury Stock [Line Items]
Partners' Capital Account, Distributions		$ 864	$ 808
Series B Preferred Stock [Member]
Equity, Class of Treasury Stock [Line Items]
Partners' Capital Account, Units, Redeemed	600,000
Dividend rate, percentage		6.875%
Preferred Stock, Redemption Price Per Share	$ 1,000
Partners' Capital Account, Distributions	$ 21
Distribution date	Feb. 15, 2023
Preferred Stock, Redemption Terms	MPLX exercised its right to redeem all 600,000 outstanding 6.875 percent Fixed-to-Floating Rate Cumulative Redeemable Perpetual Preferred Units (the “Series B preferred units”). MPLX paid unitholders the Series B preferred unit redemption price of $1,000 per unit.

Equity - Cash Distributions (De

Equity - Cash Distributions (Details) - USD ($) $ / shares in Units, $ in Millions					3 Months Ended
	May 13, 2024	May 03, 2024	Apr. 23, 2024	Feb. 15, 2023	Mar. 31, 2024	Mar. 31, 2023
Distribution Made to Limited Partner [Line Items]
Distribution Made to Limited Partner, Cash Distributions Declared					$ 874	$ 804
Cash distributions declared per limited partner common unit					$ 0.850	$ 0.775
Series A Preferred Stock [Member]
Distribution Made to Limited Partner [Line Items]
Distribution Made to Limited Partner, Cash Distributions Declared					$ 10	$ 23
Series B Preferred Stock [Member]
Distribution Made to Limited Partner [Line Items]
Distribution Made to Limited Partner, Cash Distributions Declared					0	5	[1]
Distribution date				Feb. 15, 2023
Common Unit-holders Public
Distribution Made to Limited Partner [Line Items]
Distribution Made to Limited Partner, Cash Distributions Declared					$ 864	$ 776
Subsequent Event
Distribution Made to Limited Partner [Line Items]
Distribution Made to Limited Partner, Cash Distributions Declared			$ 864
Distribution Made to Limited Partner, Declaration Date			Apr. 23, 2024
Cash distributions declared per limited partner common unit			$ 0.850
Subsequent Event | Common Unit-holders Public
Distribution Made to Limited Partner [Line Items]
Distribution date	May 13, 2024
Date of record		May 03, 2024
[1]The three months ended March 31, 2023 includes the portion of the $21 million distribution paid to the Series B preferred unitholders on February 15, 2023 that was earned during the period prior to redemption.

Net Income Per Limited Partne_4

Net Income Per Limited Partner Unit - Basic and Diluted Earnings Per Unit (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions		3 Months Ended
		Mar. 31, 2024	Mar. 31, 2023
Schedule Of Earnings Per Share Basic And Diluted [Line Items]
Income (Loss) from Continuing Operations, Net of Tax, Attributable to Parent	[1]	$ 1,005	$ 943
Undistributed Earnings (Loss) Allocated to Participating Securities, Basic		3	4
Undistributed Earnings (Loss) Allocated to Participating Securities, Diluted		3	4
Impact of redemption of Series B preferred units		0	5
Net Income (Loss) Available to Common Stockholders, Diluted		$ 992	$ 906
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount		1	1
Weighted average units outstanding:
Common - basic		1,008	1,001
Common - diluted		1,008	1,001
Net income attributable to MPLX LP per limited partner unit:
Common - basic		$ 0.98	$ 0.91
Common - diluted		$ 0.98	$ 0.91
Series A Preferred Stock [Member]
Schedule Of Earnings Per Share Basic And Diluted [Line Items]
Distributed Earnings		$ 10	$ 23
Series B Preferred Stock [Member]
Schedule Of Earnings Per Share Basic And Diluted [Line Items]
Distributed Earnings		0	5
Common Unit-holders Public
Schedule Of Earnings Per Share Basic And Diluted [Line Items]
Net Income (Loss) Available to Common Stockholders, Basic		$ 992	$ 906
[1]Allocation of net income attributable to MPLX LP assumes all earnings for the period have been distributed based on the distribution priorities applicable to the period.

Segment Information (Details)

Segment Information (Details)	3 Months Ended
	Mar. 31, 2024
Segment Reporting [Abstract]
Number of reportable segments	2

Segment Information - Segment A

Segment Information - Segment Adjusted EBITDA (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2024		Mar. 31, 2023
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		$ 2,172		$ 2,127
Sales-type lease revenue		34		34
Income from equity method investments		157		134
Revenues		2,846		2,713
Capital Expenditure		210		191
Investments in unconsolidated affiliates(3)		119		51
Investments in and Advance to Affiliates, Subsidiaries, Associates, and Joint Ventures		92
L&S
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		1,072		1,038
G&P
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		1,100		1,089
Operating Segments
Segment Reporting Information [Line Items]
Adjusted EBITDA		1,635		1,519
Operating Segments | L&S
Segment Reporting Information [Line Items]
Rental income		224		212
Sales-type lease revenue		121		125
Income from equity method investments		89		71
Other Income		50		14
Revenues	[1]	1,556		1,460
Adjusted EBITDA	[2]	1,098		1,026
Capital Expenditure		84		68
Investments in unconsolidated affiliates(3)		92	[3]	15
Operating Segments | G&P
Segment Reporting Information [Line Items]
Rental income		53		51
Sales-type lease revenue		34		34
Income from equity method investments		68		63
Other Income		35		16
Revenues	[1]	1,290		1,253
Adjusted EBITDA	[2]	537		493
Capital Expenditure		126		123
Investments in unconsolidated affiliates(3)		27		36
Service [Member] | Operating Segments | L&S
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		1,067		1,033
Service [Member] | Operating Segments | G&P
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		577		525
Product [Member] | Operating Segments | L&S
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		5		5
Product [Member] | Operating Segments | G&P
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		523		564
Third Party [Member] | L&S
Segment Reporting Information [Line Items]
Revenues		207		170
Third Party [Member] | G&P
Segment Reporting Information [Line Items]
Revenues		$ 1,212		$ 1,166
[1]Within the total segment revenues and other income amounts presented above, third party revenues for the L&S segment were $207 million and $170 million for the three months ended March 31, 2024 and March 31, 2023, respectively. Third party revenues for the G&P segment were $1,212 million and $1,166 million for the three months ended March 31, 2024 and March 31, 2023, respectively.[2]See below for the reconciliation from Segment Adjusted EBITDA to Net income.[3]The three months ended March 31, 2024 includes a contribution of $92 million to Dakota Access to fund our share of a debt repayment by the joint venture.

Segment Information - Reconcili

Segment Information - Reconciliation to Net Income (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2024	Mar. 31, 2023
Segment Reporting, Revenue Reconciling Item [Line Items]
Depreciation and Amortization	[1]	$ 317	$ 296
Net interest and other financial costs		235	243
Income from equity method investments		157	134
Net income		1,015	952
Operating Segments
Segment Reporting, Revenue Reconciling Item [Line Items]
Adjusted EBITDA		1,635	1,519
Segment Reconciling Items [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Distributions/adjustments related to equity method investments		200	153
Adjusted EBITDA attributable to noncontrolling interests		11	10
Other Noncash Income (Expense)	[2]	36	19
L&S
Segment Reporting, Revenue Reconciling Item [Line Items]
Depreciation and Amortization		130	129
L&S | Operating Segments
Segment Reporting, Revenue Reconciling Item [Line Items]
Adjusted EBITDA	[3]	1,098	1,026
Income from equity method investments		89	71
G&P
Segment Reporting, Revenue Reconciling Item [Line Items]
Depreciation and Amortization		187	167
G&P | Operating Segments
Segment Reporting, Revenue Reconciling Item [Line Items]
Adjusted EBITDA	[3]	537	493
Income from equity method investments		$ 68	$ 63
[1]Depreciation and amortization attributable to L&S was $130 million and $129 million for the three months ended March 31, 2024 and March 31, 2023, respectively. Depreciation and amortization attributable to G&P was $187 million and $167 million for the three months ended March 31, 2024 and March 31, 2023, respectively.[2]Includes unrealized derivative gain/(loss), equity-based compensation, provision for income taxes, and other miscellaneous items.[3]See below for the reconciliation from Segment Adjusted EBITDA to Net income.

Property, Plant and Equipment_2

Property, Plant and Equipment (Summary of Property, Plant and Equipment) (Details) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023
Property, Plant and Equipment [Line Items]
Gross PP&E	$ 27,694	$ 27,385
Accumulated Depreciation	8,395	8,121
Net PP&E	19,299	19,264
L&S
Property, Plant and Equipment [Line Items]
Gross PP&E	12,842	12,779
Accumulated Depreciation	4,158	4,037
Net PP&E	8,684	8,742
G&P
Property, Plant and Equipment [Line Items]
Gross PP&E	14,852	14,606
Accumulated Depreciation	4,237	4,084
Net PP&E	$ 10,615	$ 10,522

Fair Values - Recurring - Balan

Fair Values - Recurring - Balance Sheet Location Table (Details) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset, Subject to Master Netting Arrangement, before Offset	$ 0	$ 0
Derivative Liability, Subject to Master Netting Arrangement, before Offset	69	61
Fair Value, Inputs, Level 3 [Member] | Embedded Derivative Financial Instruments [Member] | Other current assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset, Subject to Master Netting Arrangement, before Offset	0	0
Fair Value, Inputs, Level 3 [Member] | Embedded Derivative Financial Instruments [Member] | Other Noncurrent Assets [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset, Subject to Master Netting Arrangement, before Offset	0	0
Fair Value, Inputs, Level 3 [Member] | Embedded Derivative Financial Instruments [Member] | Other Current Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability, Subject to Master Netting Arrangement, before Offset	13	11
Fair Value, Inputs, Level 3 [Member] | Embedded Derivative Financial Instruments [Member] | Other Noncurrent Liabilities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Liability, Subject to Master Netting Arrangement, before Offset	$ 56	$ 50

Fair Values - Recurring - Signi

Fair Values - Recurring - Significant Unobservable Inputs in Level 3 Valuation (Details)	3 Months Ended
	Mar. 31, 2024 $ / gal USD ($)
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Derivative, Average Forward Price | $ / gal	0.83
Embedded Derivative Financial Instruments [Member] | Natural Gas [Member]
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Embedded Derivative Renewal Term	5 years
Fair Value, Inputs, Level 3 [Member] | Embedded Derivative Financial Instruments [Member]
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Fair Value Inputs Probability of Renewal	100%
Minimum [Member] | Fair Value, Inputs, Level 3 [Member] | Embedded Derivative Financial Instruments [Member]
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Derivative, Forward Price	0.66
Maximum [Member] | Fair Value, Inputs, Level 3 [Member] | Embedded Derivative Financial Instruments [Member]
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Derivative, Forward Price	1.61

Changes in Level 3 Fair Value M

Changes in Level 3 Fair Value Measurements (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2024	Mar. 31, 2023
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance		$ (61)	$ (61)
Unrealized and realized (loss)/gain included in Net Income(1)	[1]	(12)	0
Settlements		4	3
Ending balance		$ (69)	$ (58)
[1](Loss)/gain on derivatives embedded in commodity contracts are recorded in Purchased product costs in the Consolidated Statements of Income.

Fair Value Measurements Gain_Lo

Fair Value Measurements Gain/Loss Included in Earnings Relating to Assets Still Held at End of Period (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Fair Value Disclosures [Abstract]
The amount of total loss for the period included in earnings attributable to the change in unrealized gain/(loss) relating to liabilities still held at end of period	$ (11)	$ 0

Fair Values - Reported (Details

Fair Values - Reported (Details) - USD ($) $ in Millions		Mar. 31, 2024	Dec. 31, 2023
Estimate of Fair Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-Term Debt, Fair Value	[1]	$ 19,206	$ 19,377
Reported Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-Term Debt, Fair Value	[1]	$ 20,557	$ 20,547
[1]Any amounts outstanding under the MPC Loan Agreement are not included in the table above, as the carrying value approximates fair value. This balance is reflected in Current liabilities - related parties in the Consolidated Balance Sheets.

Derivative Financial Instrume_3

Derivative Financial Instruments - Embedded Derivatives in Commodity Contracts (Details) - Embedded Derivative Financial Instruments [Member] $ in Millions	3 Months Ended
	Mar. 31, 2024 USD ($)	Dec. 31, 2023 USD ($)
Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member]
Derivative [Line Items]
Derivative Liability	$ (69)	$ (61)
Natural Gas [Member]
Derivative [Line Items]
Number of Renewals	1
Embedded Derivative Renewal Term	5 years

Derivative Financial Instrume_4

Derivative Financial Instruments - Derivatives Balance Sheet Location (Details) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023
Derivatives, Fair Value [Line Items]
Derivative Liability, Subject to Master Netting Arrangement, before Offset	$ 69	$ 61
Other Current Liabilities [Member] | Embedded Derivative Financial Instruments [Member] | Fair Value, Inputs, Level 3 [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Subject to Master Netting Arrangement, before Offset	13	11
Other Noncurrent Liabilities [Member] | Embedded Derivative Financial Instruments [Member] | Fair Value, Inputs, Level 3 [Member]
Derivatives, Fair Value [Line Items]
Derivative Liability, Subject to Master Netting Arrangement, before Offset	$ 56	$ 50

Derivatives Financial Instrumen

Derivatives Financial Instruments - Derivative Income Statement Location (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Derivative [Line Items]
Derivative, Gain (Loss) on Derivative, Net	$ (12)	$ 2
Derivative, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Net income	Net income
Purchased product costs
Derivative [Line Items]
Realized gain (loss)	$ (4)	$ (3)
Unrealized Gain (Loss) on Derivatives and Commodity Contracts	(8)	3
Derivative, Gain (Loss) on Derivative, Net	(12)	0
Product Sales
Derivative [Line Items]
Unrealized Gain (Loss) on Derivatives and Commodity Contracts	0	2
Derivative, Gain (Loss) on Derivative, Net	$ 0	$ 2

Debt - Summary of Outstanding B

Debt - Summary of Outstanding Borrowings (Detail) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023
Debt Instrument [Line Items]
MPLX Credit Agreement	$ 0	$ 0
Finance lease obligations	6	6
Debt and Lease Obligation	20,706	20,706
Unamortized debt issuance costs	(119)	(122)
Unamortized discount	(143)	(153)
Amounts due within one year	1,639	1,135
Total long-term debt due after one year	18,805	19,296
MPLX LP [Member]
Debt Instrument [Line Items]
Senior Notes	20,657	20,657
MarkWest [Member]
Debt Instrument [Line Items]
Senior Notes	12	12
ANDX LP [Member]
Debt Instrument [Line Items]
Senior Notes	$ 31	$ 31

Credit Agreement (Detail)

Credit Agreement (Detail) - USD ($) $ in Millions	Jul. 07, 2022	Mar. 31, 2024	Dec. 31, 2023
Debt Instrument [Line Items]
Long-term Line of Credit		$ 0	$ 0
MPLX Revolving Credit Facility due June 2027
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 2,000
Letter of Credit, Issuing Capacity	$ 150
Debt Instrument, Description of Variable Rate Basis	Adjusted Term SOFR or the Alternate Base Rate, both as defined in the MPLX Credit Agreement, plus an applicable margin.

Senior Notes (Details)

Senior Notes (Details) - Senior Notes [Member]	Mar. 31, 2024
Minimum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	1.75%
Maximum [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	5.65%

Interest and Other Financial _3

Interest and Other Financial Costs (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Other Income and Expenses [Abstract]
Interest expense	$ 228	$ 227
Other financial costs	26	27
Interest income	(15)	(8)
Capitalized interest	(4)	(3)
Interest and Debt Expense, Total	$ 235	$ 243

Revenue Disaggregation of Reven

Revenue Disaggregation of Revenue (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2024	Mar. 31, 2023
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		$ 2,172	$ 2,127
Revenue Not from Contract with Customer, Other	[1]	674	586
Revenues		2,846	2,713
L&S
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		1,072	1,038
L&S | Operating Segments
Disaggregation of Revenue [Line Items]
Revenues	[2]	1,556	1,460
G&P
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		1,100	1,089
G&P | Operating Segments
Disaggregation of Revenue [Line Items]
Revenues	[2]	1,290	1,253
Service [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax, Third parties		658	605
Revenue from Contract with Customer, Excluding Assessed Tax, Related Parties		986	953
Service [Member] | L&S
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax, Third parties		85	83
Revenue from Contract with Customer, Excluding Assessed Tax, Related Parties		982	950
Service [Member] | L&S | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		1,067	1,033
Service [Member] | G&P
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax, Third parties		573	522
Revenue from Contract with Customer, Excluding Assessed Tax, Related Parties		4	3
Service [Member] | G&P | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		577	525
Service, Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax, Third parties		95	79
Service, Other [Member] | L&S
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax, Third parties		0	0
Service, Other [Member] | G&P
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax, Third parties		95	79
Product [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax, Third parties		370	420
Revenue from Contract with Customer, Excluding Assessed Tax, Related Parties		63	70
Product [Member] | L&S
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax, Third parties		2	2
Revenue from Contract with Customer, Excluding Assessed Tax, Related Parties		3	3
Product [Member] | L&S | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		5	5
Product [Member] | G&P
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax, Third parties		368	418
Revenue from Contract with Customer, Excluding Assessed Tax, Related Parties		60	67
Product [Member] | G&P | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		$ 523	$ 564
[1]Non-ASC 606 Revenue includes rental income, sales-type lease revenue, income from equity method investments, and other income.[2]Within the total segment revenues and other income amounts presented above, third party revenues for the L&S segment were $207 million and $170 million for the three months ended March 31, 2024 and March 31, 2023, respectively. Third party revenues for the G&P segment were $1,212 million and $1,166 million for the three months ended March 31, 2024 and March 31, 2023, respectively.

Revenue Contract Balances (Deta

Revenue Contract Balances (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2024	Mar. 31, 2023	Dec. 31, 2023	Dec. 31, 2022
Contract assets		$ 2	$ 16	$ 3	$ 21
Contract assets, additions/(deletions)		(1)	(5)
Contract with Customer, Asset, Reclassified to Receivable	[1]	0	0
Long-term contract assets		1	0	1	1
Contract with Customer, Asset Increase (Decrease), Noncurrent		0	(1)
Contract With Customer Non Current Asset Reclassified To Receivable [Line Items]	[1]	0	0
Long-term deferred revenue		349		347
Long-term contract liabilities			0		2
Contract Liability, Noncurrent, Period Increase (Decrease)			(2)
Contract Liability, Noncurrent, Revenue Recognized	[1]		0
Liability, change in timeframe, performance obligation satisfied, revenue recognized		0	0
Contract with Customer, Liability, Current			1		0
Contract Liability, Current, Period Increase (Decrease)			1
Contract Liability, Current, Revenue Recognized			0
Nonrelated Party [Member]
Deferred revenue		66	45	59	57
Deferred revenue, revenue recognized	[1]	(12)	(14)
Deferred Revenue, Additions		19	2
Long-term deferred revenue		346	231	344	216
Long-term deferred revenue, additions/(deletions)		2	15
Long-term deferred revenue, revenue recognized	[1]	0	0
Related Party [Member]
Deferred revenue		89		81
Deferred revenue, revenue recognized	[1]	(20)	(26)
Deferred Revenue, Additions		27	32
Deferred Revenue from Contracts with Customers, Current		54	69	47	63
Long-term deferred revenue		95		99
Long-term deferred revenue, additions/(deletions)		0	1
Long-term deferred revenue, revenue recognized	[1]	0	0
Deferred Revenue from Contracts with Customers, Noncurrent		$ 29	$ 26	$ 29	$ 25
[1]No significant revenue was recognized related to past performance obligations in the current periods.

Revenue Remaining Performance O

Revenue Remaining Performance Obligations (Details) $ in Millions	Mar. 31, 2024 USD ($)
Revenue from Contract with Customer [Abstract]
Contract with customer, liability	$ 495
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Revenue, Remaining Performance Obligation, Amount	$ 8,100
Maximum [Member]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation, expected timing of satisfaction, years	21 years
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2024-04-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation, expected timing of satisfaction, years	9 months
Revenue, Remaining Performance Obligation, Amount	$ 1,500
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2025-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation, expected timing of satisfaction, years	1 year
Revenue, Remaining Performance Obligation, Amount	$ 2,000
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2026-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation, expected timing of satisfaction, years	1 year
Revenue, Remaining Performance Obligation, Amount	$ 1,800
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2027-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation, expected timing of satisfaction, years	1 year
Revenue, Remaining Performance Obligation, Amount	$ 1,700
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2028-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation, expected timing of satisfaction, years	1 year
Revenue, Remaining Performance Obligation, Amount	$ 500
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2029-01-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation, expected timing of satisfaction, years	15 years
Revenue, Remaining Performance Obligation, Amount	$ 600

Supplemental Cash Flow Inform_3

Supplemental Cash Flow Information - Summary of Supplemental Cash Flow Information (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Supplemental Cash Flow Elements [Abstract]
Interest paid (net of amounts capitalized)	$ 278	$ 270
Income taxes paid	0	1
Operating Lease, Payments	19	19
Net transfers of property, plant and equipment (to)/from materials and supplies inventory	(1)	9
Property, Plant and Equipment, Transfers and Changes	25	28
Right-of-Use Asset Obtained in Exchange for Operating Lease Liability	$ 34	$ 2

Supplemental Cash Flow Inform_4

Supplemental Cash Flow Information - Summary of Reconciliation of Additions to Property, Plant and Equipment to Total Capital Expenditures (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Supplemental Cash Flow Elements [Abstract]
Additions to property, plant and equipment	$ 255	$ 169
(Decrease)/Increase in capital accruals	(45)	22
Total capital expenditures	$ 210	$ 191

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail) - USD ($) $ in Millions		1 Months Ended	3 Months Ended
	Dec. 15, 2020	Jul. 31, 2020	Mar. 31, 2024	Dec. 31, 2023
Commitments And Contingencies [Line Items]
Accrued liabilities for environmental remediation			$ 17	$ 19
Environmental Loss Contingency, Statement of Financial Position [Extensible Enumeration]			Other long-term liabilities, Other current liabilities	Other long-term liabilities, Other current liabilities
Loss Contingency, Damages Sought, Value		$ 187
Loss Contingency, Damages Paid, Value	$ 4
Guarantor Obligations, Origin and Purpose			Guarantees related to indebtedness of equity method investeesWe hold a 9.19 percent indirect interest in Dakota Access, which owns and operates the Bakken Pipeline system. In 2020, the U.S. District Court for the District of Columbia (the “D.D.C.”) ordered the United States Army Corps of Engineers (“Army Corps”), which granted permits and an easement for the Bakken Pipeline system, to prepare an environmental impact statement (“EIS”) relating to an easement under Lake Oahe in North Dakota. The D.D.C. later vacated the easement. The Army Corps issued a draft EIS in September 2023 detailing various options for the easement going forward, including denying the easement, approving the easement with additional measures, rerouting the easement, or approving the easement with no changes. The Army Corps has not selected a preferred alternative, but will make a decision in its final review, after considering input from the public and other agencies. The pipeline remains operational while the Army Corps finalizes its decision which is expected to be issued by the end of 2024.We have entered into a Contingent Equity Contribution Agreement whereby MPLX LP, along with the other joint venture owners in the Bakken Pipeline system, has agreed to make equity contributions to the joint venture upon certain events occurring to allow the entities that own and operate the Bakken Pipeline system to satisfy their senior note payment obligations. The senior notes were issued to repay amounts owed by the pipeline companies to fund the cost of construction of the Bakken Pipeline system. If the vacatur of the easement results in a temporary shutdown of the pipeline, MPLX would have to contribute its 9.19 percent pro rata share of funds required to pay interest accruing on the notes and any portion of the principal that matures while the pipeline is shutdown. MPLX also expects to contribute its 9.19 percent pro rata share of any costs to remediate any deficiencies to reinstate the easement and/or return the pipeline into operation. If the vacatur of the easement results in a permanent shutdown of the pipeline, MPLX would have to contribute its 9.19 percent pro rata share of the cost to redeem the bonds (including the one percent redemption premium required pursuant to the indenture governing the notes) and any accrued and unpaid interest. As of March 31, 2024, our maximum potential undiscounted payments under the Contingent Equity Contribution Agreement were approximately $170 million.
Financial Guarantee [Member] | Bakken Pipeline System [Member] | Guarantee of Indebtedness of Others [Member]
Commitments And Contingencies [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted			$ 170