MPLX (MPLX) 10-Q 2 May 23 2023 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2023	Apr. 26, 2023
Cover [Abstract]
Entity Central Index Key	0001552000
Current Fiscal Year End Date	--12-31
Document Fiscal Year Focus	2023
Document Fiscal Period Focus	Q1
Amendment Flag	false
Document Type	10-Q
Document Quarterly Report	true
Document Period End Date	Mar. 31, 2023
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	421-2414
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 Common Stock, Shares Outstanding		1,001,168,883

Consolidated Statements of Inco

Consolidated Statements of Income - USD ($) shares in Millions, $ in Millions		3 Months Ended
		Mar. 31, 2023	Mar. 31, 2022
Sales-type lease revenue		$ 34	$ 0
Sales-type lease revenue - related parties		125	111
Income from equity method investments		134	99
Total revenues and other income		2,713	2,610
Costs and Expenses, Related Party		361	319
Depreciation and amortization	[1]	296	313
General and administrative expenses		89	78
Other taxes		30	34
Total costs and expenses		1,517	1,550
Operating Income (Loss)		1,196	1,060
Interest expense, net of amounts capitalized		224	198
Other financial costs		19	20
Income before income taxes		953	838
Provision for income taxes		1	5
Net income		952	833
Less: Net income attributable to noncontrolling interests		9	8
Net income attributable to MPLX LP	[2]	943	825
Limited partners' interest in net income attributable to MPLX LP		$ 915	$ 793
Net income attributable to MPLX LP per limited partner unit:
Common - basic		$ 0.91	$ 0.78
Common - diluted		$ 0.91	$ 0.78
Weighted average limited partner units outstanding:
Common - basic		1,001	1,015
Common - diluted		1,001	1,015
Nonrelated Party [Member]
Rental income		$ 61	$ 91
Other Income		3	(17)
Rental cost of sales		20	37
Related Party [Member]
Rental income		202	165
Other Income		27	27
Rental cost of sales		7	15
General and administrative expenses		64	55
Related-party interest and other financial costs		0	4
Service [Member]
Revenue from Contract with Customer, Excluding Assessed Tax		605	554
Revenue from Contract with Customer, Excluding Assessed Tax, Related Parties		953	915
Service, Other [Member]
Revenue from Contract with Customer, Excluding Assessed Tax		79	123
Product [Member]
Revenue from Contract with Customer, Excluding Assessed Tax		420	497
Revenue from Contract with Customer, Excluding Assessed Tax, Related Parties		70	45
Oil and Gas, Refining and Marketing [Member]
Cost of Goods and Services Sold		308	287
Natural Gas, Midstream [Member]
Cost of Goods and Services Sold		406	467
Series A Preferred Stock [Member]
Net income attributable to MPLX LP	[2]	27	23
Dividends, Preferred Stock		23	21
Series B Preferred Stock [Member]
Net income attributable to MPLX LP	[2]	5	11
Dividends, Preferred Stock		5	11
Common Stock [Member]
Net income attributable to MPLX LP	[2]	$ 911	$ 791
[1]Depreciation and amortization attributable to L&S was $129 million and $130 million for the three months ended March 31, 2023 and March 31, 2022 , respectively. Depreciation and amortization attributable to G&P was $167 million and $183 million for the three months ended March 31, 2023 and March 31, 2022, respectively.(2)    Includes unrealized derivative gain/(loss), non-cash equity-based compensation, provision for income taxes, and other miscellaneous items.[2]Allocation of net income attributable to MPLX LP assumes all earnings for the period had been distributed based on the distribution priorities applicable to the period.

Consolidated Statements of Comp

Consolidated Statements of Comprehensive Income - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Net income	$ 952	$ 833
Comprehensive income	956	842
Less comprehensive income attributable to:
Noncontrolling interests	9	8
Comprehensive income attributable to MPLX LP	947	834
Accumulated Defined Benefit Plans Adjustment Including Portion Attributable to Noncontrolling Interest
Other Comprehensive Income (Loss), Net of Tax	$ 4	$ 9

Consolidated Balance Sheets

Consolidated Balance Sheets - USD ($) $ in Millions		Mar. 31, 2023	Dec. 31, 2022
Assets
Cash and cash equivalents		$ 393	$ 238
Receivables, net		714	737
Inventories		141	148
Other current assets		63	53
Total current assets		2,012	1,905
Equity method investments		4,144	4,095
Property, Plant, and Equipment and Finance Lease Right-of-Use Asset, after Accumulated Depreciation and Amortization		18,758	18,848
Intangibles, net		673	705
Goodwill		7,645	7,645
Other noncurrent assets		954	959
Total assets		35,672	35,665
Liabilities
Accounts payable		139	224
Accrued liabilities		266	269
Accrued property, plant and equipment		158	128
Long-term debt due within one year		1	988
Interest Payable, Current		192	237
Operating lease liabilities		45	46
Total current liabilities		1,312	2,401
Long-term deferred revenue		233	219
Long-term debt		20,393	18,808
Deferred income taxes		13	13
Long-term operating lease liabilities		221	230
Other long-term liabilities		114	142
Total liabilities		22,624	22,151
Commitments and contingencies (see Note 14)
Equity
Accumulated other comprehensive loss		(4)	(8)
Total MPLX LP partners’ capital		11,843	12,309
Noncontrolling interests		237	237
Total equity		12,080	12,546
Total liabilities, preferred units and equity		35,672	35,665
Related Party [Member]
Liabilities
Other current liabilities		327	343
Nonrelated Party [Member]
Assets
Right of use assets, net		274	283
Liabilities
Other current liabilities		184	166
Related Party [Member]
Assets
Receivables, net		559	610
Current assets - related parties		701	729
Other current assets		4	3
Right of use assets, net		228	228
Noncurrent assets - related parties		1,212	1,225
Liabilities
Accounts payable	[1]	239	262
Operating lease liabilities		1	1
Other current liabilities		327	343
Long-term deferred revenue		111	110
Other Liabilities, Noncurrent		338	338
Long-term operating lease liabilities		227	228
Equity
Limited Partners' Capital Account		3,388	3,293
Nonrelated Party [Member]
Liabilities
Long-term deferred revenue		231	216
Equity
Limited Partners' Capital Account		8,459	8,413
Series A Preferred Stock [Member]
Liabilities
Temporary Equity, Carrying Amount, Including Portion Attributable to Noncontrolling Interests		968	968
Series B Preferred Stock [Member]
Equity
Preferred Units, Preferred Partners' Capital Accounts		$ 0	$ 611
[1]There were no borrowings outstanding on the MPC Loan Agreement as of March 31, 2023 or December 31, 2022.

Consolidated Balance Sheets (Pa

Consolidated Balance Sheets (Parenthetical) - shares	Mar. 31, 2023	Dec. 31, 2022
Units Outstanding	1,001,163,358	1,001,020,616
Series B Preferred Stock [Member]
Preferred Units, Issued	0	600,000
Preferred Units, Outstanding	0	600,000
Series A Preferred Stock [Member]
Preferred Units, Issued	30,000,000	30,000,000
Preferred Units, Outstanding	30,000,000	30,000,000
Common Stock [Member] | Nonrelated Party [Member]
Units issued	354,000,000	354,000,000
Units Outstanding	354,000,000	354,000,000
Common Stock [Member] | Related Party [Member]
Units issued	647,000,000	647,000,000
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, 2023	Mar. 31, 2022
Operating activities:
Net income		$ 952	$ 833
Adjustments to reconcile net income to net cash provided by operating activities:
Amortization of deferred financing costs		17	18
Depreciation and amortization	[1]	296	313
Deferred income taxes		0	4
Loss on disposal of assets		0	18
Income from equity method investments		(134)	(99)
Distributions from unconsolidated affiliates		140	120
Change in fair value of derivatives		(5)	(9)
Changes in:
Receivables		38	(87)
Inventories		(2)	(7)
Accounts payable and accrued liabilities		(130)	73
Assets/liabilities - related parties		44	(112)
Right of use assets/operating lease liabilities		(1)	(1)
Deferred revenue		3	16
All other, net		9	45
Net cash provided by operating activities		1,227	1,125
Net Cash Provided by (Used in) Investing Activities [Abstract]
Additions to property, plant and equipment		(169)	(169)
Disposal of assets		0	3
Investments in unconsolidated affiliates		(51)	(110)
Net cash used in investing activities		(220)	(276)
Net Cash Provided by (Used in) Financing Activities [Abstract]
Long-term debt borrowings		1,589	2,385
Long-term debt - repayments		(1,000)	(1,201)
Debt issuance costs		15	16
Unit repurchases		0	(100)
Distributions to noncontrolling interests		(10)	(9)
Distributions to unitholders and general partner		(777)	(716)
Contributions from MPC		8	10
All other, net		(3)	(4)
Net cash used in financing activities		(852)	(820)
Net change in cash, cash equivalents and restricted cash		155	29
Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents, Beginning Balance		238	13
Cash, Cash Equivalents, Restricted Cash, and Restricted Cash Equivalents, Ending Balance		393	42
Revolving Credit Facility
Net Cash Provided by (Used in) Financing Activities [Abstract]
Related party debt borrowings		0	1,849
Related party debt repayments		0	(2,976)
Series A Preferred Stock [Member]
Net Cash Provided by (Used in) Financing Activities [Abstract]
Distributions to preferred unitholders		(23)	(21)
Series B Preferred Stock [Member]
Net Cash Provided by (Used in) Financing Activities [Abstract]
Redemption of Series B preferred units		(600)	0
Distributions to preferred unitholders		$ (21)	$ (21)
[1]Depreciation and amortization attributable to L&S was $129 million and $130 million for the three months ended March 31, 2023 and March 31, 2022 , respectively. Depreciation and amortization attributable to G&P was $167 million and $183 million for the three months ended March 31, 2023 and March 31, 2022, respectively.(2)    Includes unrealized derivative gain/(loss), non-cash equity-based compensation, provision for income taxes, and other miscellaneous items.

Consolidated Statements of Equi

Consolidated Statements of Equity - USD ($) $ in Millions	Total	Nonrelated Party [Member]	Related Party [Member]	Series B Preferred Stock [Member]	Series A Preferred Stock [Member]	AOCI Attributable to Parent [Member]	Noncontrolling Interest [Member]
Preferred Units, Preferred Partners' Capital Accounts				$ 611
Limited Partners' Capital Account		$ 8,579	$ 2,638
Noncontrolling interests							$ 241
Accumulated other comprehensive loss						$ (17)
Temporary Equity, Carrying Amount, Including Portion Attributable to Noncontrolling Interests					$ 965
Beginning Balance at Dec. 31, 2021	$ 12,052
Net income	812	287	506	11		0	8
Stock Repurchased and Retired During Period, Value	(100)	(100)	0	0	0	0	0
Distributions	(746)	(260)	(456)	(21)	(21)	0	(9)
Contributions	10	0	10	0	0	0	0
Other	8	(1)	0	0		9	0
Ending Balance at Mar. 31, 2022	12,036
Temporary Equity, Net Income					21
Temporary Equity, Other Changes					0
Preferred Units, Preferred Partners' Capital Accounts				601
Limited Partners' Capital Account		8,505	2,698
Noncontrolling interests							240
Accumulated other comprehensive loss						(8)
Temporary Equity, Carrying Amount, Including Portion Attributable to Noncontrolling Interests					965
Preferred Units, Preferred Partners' Capital Accounts				611
Limited Partners' Capital Account		8,413	3,293
Noncontrolling interests	237						237
Accumulated other comprehensive loss	(8)					(8)
Temporary Equity, Carrying Amount, Including Portion Attributable to Noncontrolling Interests					968
Beginning Balance at Dec. 31, 2022	12,546
Net income	929	323	592	5		0	9
Redemption of Series B preferred units	(600)	(2)	(3)	(595)	0	0	0
Distributions	(808)	(275)	(502)	(21)	(23)	0	(10)
Contributions	8	0	8	0	0	0	0
Other	5	0	0	0		4	1
Ending Balance at Mar. 31, 2023	12,080
Temporary Equity, Net Income					23
Temporary Equity, Other Changes					0
Preferred Units, Preferred Partners' Capital Accounts				$ 0
Limited Partners' Capital Account		$ 8,459	$ 3,388
Noncontrolling interests	237						$ 237
Accumulated other comprehensive loss	$ (4)					$ (4)
Temporary Equity, Carrying Amount, Including Portion Attributable to Noncontrolling Interests					$ 968

Description of the Business and

Description of the Business and Basis of Presentation	3 Months Ended
	Mar. 31, 2023
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. References in this report to “MPLX LP,” “MPLX,” “the Partnership,” “we,” “ours,” “us,” or like terms refer to MPLX LP and its subsidiaries. References to our sponsor and customer, “MPC,” refer collectively to Marathon Petroleum Corporation and its subsidiaries, other than the Partnership. 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 7 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, 2022. The results of operations for the three months ended March 31, 2023 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.

Accounting Standards

Accounting Standards	3 Months Ended
	Mar. 31, 2023
Accounting Standards Update and Change in Accounting Principle [Abstract]
Accounting Standards	Accounting Standards Not Yet Adopted ASU 2023-01, Leases (Topic 842): Common Control Arrangements In March 2023, the FASB issued an ASU to amend certain provisions of ASC 842 that apply to arrangements between related parties under common control. The ASU amends the accounting for the amortization period of leasehold improvements in common-control leases for all entities and requires certain disclosures when the lease term is shorter than the useful life of the asset. This ASU is effective for fiscal years beginning after December 15, 2023, including interim periods within those fiscal years. Early adoption is permitted. We do not expect the application of this ASU to have a material impact on our consolidated financial statements or financial disclosures.

Investments and Noncontrolling

Investments and Noncontrolling Interest	3 Months Ended
	Mar. 31, 2023
Equity Method Investments and Joint Ventures [Abstract]
Investments and Noncontrolling Interests	Investments and Noncontrolling Interests The following table presents MPLX’s equity method investments at the dates indicated: Ownership as of Carrying value at March 31, March 31, December 31, (In millions, except ownership percentages) VIE 2023 2023 2022 L&S Andeavor Logistics Rio Pipeline LLC X 67% $ 176 $ 177 Illinois Extension Pipeline Company, L.L.C. 35% 243 236 LOOP LLC 41% 292 287 MarEn Bakken Company LLC (1) 25% 466 475 Minnesota Pipe Line Company, LLC 17% 177 178 Whistler Pipeline LLC 38% 217 211 Other (2) X 289 269 Total L&S 1,860 1,833 G&P Centrahoma Processing LLC 40% 129 131 MarkWest EMG Jefferson Dry Gas Gathering Company, L.L.C X 67% 336 335 MarkWest Torñado GP, L.L.C. X 60% 312 306 MarkWest Utica EMG, L.L.C. X 58% 692 669 Rendezvous Gas Services, L.L.C. X 78% 135 137 Sherwood Midstream Holdings LLC X 51% 122 125 Sherwood Midstream LLC X 50% 509 512 Other (2) X 49 47 Total G&P 2,284 2,262 Total $ 4,144 $ 4,095 (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 or DAPL. (2) Some investments included within Other have also been deemed to be VIEs. For those entities that have been deemed to be VIEs, neither MPLX nor any of its subsidiaries have been deemed to be the primary beneficiary due to voting rights on significant matters. While we have the ability to exercise influence through participation in the management committees which make all significant decisions, we have equal influence over each committee as a joint interest partner and all significant decisions require the consent of the other investors without regard to economic interest. As such, we have determined that these entities should not be consolidated and applied the equity method of accounting with respect to our investments in each entity. Sherwood Midstream LLC (“Sherwood Midstream”) has been deemed the primary beneficiary of Sherwood Midstream Holdings LLC (“Sherwood Midstream Holdings”) due to its controlling financial interest through its authority to manage the joint venture. As a result, Sherwood Midstream consolidates Sherwood Midstream Holdings. Therefore, MPLX also reports its portion of Sherwood Midstream Holdings’ net assets as a component of its investment in Sherwood Midstream. As of March 31, 2023, MPLX had a 24.54 percent indirect ownership interest in Sherwood Midstream Holdings through Sherwood Midstream. MPLX’s maximum exposure to loss as a result of its involvement with equity method investments includes its equity investment, any additional capital contribution commitments and any operating expenses incurred by the subsidiary operator in excess of its compensation received for the performance of the operating services. MPLX did not provide any financial support to equity method investments that it was not contractually obligated to provide during the three months ended March 31, 2023. See Note 14 for information on our Guarantees related to indebtedness of equity method investees.

Related Party Agreements and Tr

Related Party Agreements and Transactions	3 Months Ended
	Mar. 31, 2023
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; as well as 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 agreement. 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 delivers shrink gas to the producers on our behalf. We pay MPC a marketing fee in exchange for assuming the commodity risk. Additionally, MPLX has obligations to MPC for services provided to MPLX by MPC under omnibus and employee services-type agreements as well as 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 11. There was no activity on the MPC Loan Agreement for the three months ended March 31, 2023. Related Party Revenue Related party sales to MPC primarily consist of crude oil and refined products pipeline and trucking transportation 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 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, 2023 and March 31, 2022, these sales totaled $198 million and $293 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, 2023 and March 31, 2022, General and administrative expenses incurred from MPC totaled $64 million and $55 million, respectively. Some charges incurred under the omnibus and employee service agreements are related to engineering 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, 2023 and March 31, 2022, these charges totaled $10 million and $19 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 $ 559 $ 610 Lease receivables 121 111 Prepaid 17 5 Other 4 3 Total 701 729 Noncurrent assets - related parties Long-term lease receivables 865 883 Right of use assets 228 228 Unguaranteed residual asset 95 87 Long-term receivables 24 27 Total 1,212 1,225 Current liabilities - related parties MPC loan agreement and other payables (1) 239 262 Deferred revenue 87 80 Operating lease liabilities 1 1 Total 327 343 Long-term liabilities - related parties Long-term operating lease liabilities 227 228 Long-term deferred revenue 111 110 Total $ 338 $ 338 (1) There were no borrowings outstanding on the MPC Loan Agreement as of March 31, 2023 or December 31, 2022. Other Related Party Transactions

Equity

Equity	3 Months Ended
	Mar. 31, 2023
Equity [Abstract]
Equity	Equity The changes in the number of common units during the three months ended March 31, 2023 are summarized below: (In units) Common Units Balance at December 31, 2022 1,001,020,616 Unit-based compensation awards 142,742 Balance at March 31, 2023 1,001,163,358 Unit Repurchase Program On August 2, 2022, we announced the board authorization for the repurchase of up to an additional $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 discontinued at any time. No units were repurchased during the three months ended March 31, 2023. As of March 31, 2023, we had $846 million remaining under the unit repurchase authorization. Redemption of the Series B Preferred Units On February 15, 2023, MPLX exercised its right to redeem all 600,000 outstanding units of 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. Distributions on the Series B preferred units were payable semi-annually in arrears on the 15th day, or the first business day thereafter, of February and August of each year up to and including February 15, 2023. In accordance with these terms, MPLX made a final cash distribution of $21 million to Series B preferred unitholders on February 15, 2023, in conjunction with the redemption. The changes in the Series B preferred unit balance during the three months ended March 31, 2023 and March 31, 2022 are included in the Consolidated Statements of Equity within Series B preferred units. Distributions On April 25, 2023, MPLX declared a cash distribution for the first quarter of 2023, totaling $776 million, or $0.775 per common unit. This distribution will be paid on May 15, 2023 to common unitholders of record on May 5, 2023. This rate will also be received by Series A preferred unitholders. Quarterly distributions for 2023 and 2022 are summarized below: (Per common unit) 2023 2022 March 31, $ 0.775 $ 0.705 The allocation of total quarterly cash distributions to limited and preferred unitholders is as follows for the three months ended March 31, 2023 and March 31, 2022. 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) 2023 2022 Common and preferred unit distributions: Common unitholders, includes common units of general partner $ 776 $ 713 Series A preferred unit distributions 23 21 Series B preferred unit distributions (1) 5 11 Total cash distributions declared $ 804 $ 745 (1) Represents the portion of the $21 million distribution paid to the Series B preferred unitholders on February 15, 2023 that was earned during the three months ended March 31, 2023.

Net Income Per Limited Partner

Net Income Per Limited Partner Unit	3 Months Ended
	Mar. 31, 2023
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, 2023 and March 31, 2022, MPLX had participating securities consisting of common units, certain equity-based compensation awards, Series A preferred units and Series B preferred units and 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, 2023 and March 31, 2022 were less than 1 million. Three Months Ended (In millions) 2023 2022 Net income attributable to MPLX LP $ 943 $ 825 Less: Distributions declared on Series A preferred units 23 21 Distributions declared on Series B preferred units 5 11 Limited partners’ distributions declared on MPLX common units (including common units of general partner) 776 713 Undistributed net gain attributable to MPLX LP $ 139 $ 80 Three Months Ended March 31, 2023 (In millions, except per unit data) Limited Partners’ Series A Preferred Units Series B Preferred Units Total Basic and diluted net income attributable to MPLX LP per unit Net income attributable to MPLX LP: Distributions declared $ 776 $ 23 $ 5 $ 804 Undistributed net gain attributable to MPLX LP 135 4 — 139 Net income attributable to MPLX LP (1) 911 $ 27 $ 5 943 Impact of redemption of Series B preferred units (5) (5) Income available to common unitholders $ 906 $ 938 Weighted average units outstanding: Basic 1,001 Diluted 1,001 Net income attributable to MPLX LP per limited partner unit: Basic $ 0.91 Diluted $ 0.91 (1) Allocation of net income attributable to MPLX LP assumes all earnings for the period had been distributed based on the distribution priorities applicable to the period. Three Months Ended March 31, 2022 (In millions, except per unit data) Limited Partners’ Series A Preferred Units Series B Preferred Units Total Basic and diluted net income attributable to MPLX LP per unit Net income attributable to MPLX LP: Distributions declared $ 713 $ 21 $ 11 $ 745 Undistributed net gain attributable to MPLX LP 78 2 — 80 Net income attributable to MPLX LP (1) $ 791 $ 23 $ 11 $ 825 Weighted average units outstanding: Basic 1,015 Diluted 1,015 Net income attributable to MPLX LP per limited partner unit: Basic $ 0.78 Diluted $ 0.78 (1) Allocation of net income attributable to MPLX LP assumes all earnings for the period had been distributed based on the distribution priorities applicable to the period.

Segment Information

Segment Information	3 Months Ended
	Mar. 31, 2023
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) interest and other financial costs; (iii) income/(loss) from equity method investments; (iv) distributions and adjustments related to equity method investments; (v) gain on sales-type leases; (vi) impairment expense; (vii) noncontrolling interests; and (viii) 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) 2023 2022 L&S Service revenue $ 1,033 $ 983 Rental income 212 175 Product related revenue 5 4 Sales-type lease revenue 125 111 Income from equity method investments 71 52 Other income 14 12 Total segment revenues and other income (1) 1,460 1,337 Segment Adjusted EBITDA (2) 1,026 904 Capital expenditures 68 77 Investments in unconsolidated affiliates 15 68 G&P Service revenue 525 486 Rental income 51 81 Product related revenue 564 661 Sales-type lease revenue 34 — Income from equity method investments 63 47 Other income (loss) 16 (2) Total segment revenues and other income (1) 1,253 1,273 Segment Adjusted EBITDA (2) 493 489 Capital expenditures 123 95 Investments in unconsolidated affiliates $ 36 $ 42 (1) Within the total segment revenues and other income amounts presented above, third party revenues for the L&S segment were $170 million and $135 million for the three months ended March 31, 2023 and March 31, 2022, respectively. Third party revenues for the G&P segment were $1,166 million and $1,212 million for the three months ended March 31, 2023 and March 31, 2022, respectively. (2) See below for the reconciliation from Segment Adjusted EBITDA to Net income. The table below provides a reconciliation between Net income and Segment Adjusted EBITDA. Three Months Ended (In millions) 2023 2022 Reconciliation to Net income: L&S Segment Adjusted EBITDA $ 1,026 $ 904 G&P Segment Adjusted EBITDA 493 489 Total reportable segments 1,519 1,393 Depreciation and amortization (1) (296) (313) Interest and other financial costs (243) (222) Income from equity method investments 134 99 Distributions/adjustments related to equity method investments (153) (132) Adjusted EBITDA attributable to noncontrolling interests 10 9 Other (2) (19) (1) Net income $ 952 $ 833 (1) Depreciation and amortization attributable to L&S was $129 million and $130 million for the three months ended March 31, 2023 and March 31, 2022 , respectively. Depreciation and amortization attributable to G&P was $167 million and $183 million for the three months ended March 31, 2023 and March 31, 2022, respectively.

Property, Plant and Equipment

Property, Plant and Equipment	3 Months Ended
	Mar. 31, 2023
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, 2023 December 31, 2022 (In millions) Gross PP&E Accumulated Depreciation Net PP&E Gross PP&E Accumulated Depreciation Net PP&E L&S $ 12,476 $ 3,673 $ 8,803 $ 12,416 $ 3,554 $ 8,862 G&P 13,607 3,652 9,955 13,495 3,509 9,986 Total $ 26,083 $ 7,325 $ 18,758 $ 25,911 $ 7,063 $ 18,848 We capitalize interest as part of the cost of major projects during the construction period. Capitalized interest totaled $3 million and $2 million for the three months ended March 31, 2023 and March 31, 2022, respectively.

Fair Value Measurements

Fair Value Measurements	3 Months Ended
	Mar. 31, 2023
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, 2023 and December 31, 2022 by fair value hierarchy level. March 31, 2023 December 31, 2022 (In millions) Asset Liability Asset Liability Commodity contracts (Level 2) Other current assets / Other current liabilities $ 2 $ — $ — $ — Embedded derivatives in commodity contracts (Level 3) Other current assets / Other current liabilities — 11 — 10 Other noncurrent assets / Other long-term liabilities — 47 — 51 Total carrying value in Consolidated Balance Sheets $ 2 $ 58 $ — $ 61 Level 2 instruments include over-the-counter fixed swaps to mitigate the price risk from our sales of propane. The swap valuations are based on observable inputs in the form of forward prices based on Mont Belvieu propane forward spot prices and contain no significant unobservable inputs. 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 $0.58 to $1.55 per gallon with a weighted average of $0.77 per gallon and (2) the probability of renewal of 100 percent 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) 2023 2022 Beginning balance $ (61) $ (108) Unrealized and realized gain included in Net Income (1) — 4 Settlements 3 5 Ending balance $ (58) $ (99) The amount of total gain/(loss) for the period included in earnings attributable to the change in unrealized gain/(loss) relating to liabilities still held at end of period $ — $ 5 (1) Gain/(loss) on derivatives embedded in commodity contracts are recorded in Purchased product costs in the Consolidated Statements of Income. 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 10). 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, 2023 December 31, 2022 (In millions) Fair Value Carrying Value Fair Value Carrying Value Outstanding debt (1) $ 19,167 $ 20,517 $ 18,095 $ 19,905 (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 2 instruments include over-the-counter fixed swaps to mitigate the price risk from our sales of propane. The swap valuations are based on observable inputs in the form of forward prices based on Mont Belvieu propane forward spot prices and contain no significant unobservable inputs. 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 $0.58 to $1.55 per gallon with a weighted average of $0.77 per gallon and (2) the probability of renewal of 100 percent for the five

Derivative Financial Instrument

Derivative Financial Instruments	3 Months Ended
	Mar. 31, 2023
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Derivative Disclosure	Derivatives As of March 31, 2023, MPLX had the following outstanding commodity contracts that were executed to manage the price risk associated with sales of propane during 2023: Derivative contracts not designated as hedging instruments Financial Position Notional Quantity Propane (gal) Short 33,970,000 Embedded Derivative - MPLX has a natural gas purchase commitment embedded in a keep-whole processing agreement with a producer customer in the Southern Appalachian 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, 2023 and December 31, 2022, 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) 2023 2022 Product sales: Unrealized gain $ 2 $ — Product sales derivative gain 2 — Purchased product costs: Realized loss (3) (5) Unrealized gain 3 9 Purchased product cost derivative gain — 4 Total derivative gain included in Net income $ 2 $ 4

Debt

Debt	3 Months Ended
	Mar. 31, 2023
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 20,046 Consolidated subsidiaries: MarkWest 12 23 ANDX 31 31 Financing lease obligations 7 8 Total 20,707 20,108 Unamortized debt issuance costs (130) (117) Unamortized discount (183) (195) Amounts due within one year (1) (988) Total long-term debt due after one year $ 20,393 $ 18,808 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, 2023. 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. On February 9, 2023, MPLX issued $1.6 billion aggregate principal amount of notes, consisting of $1.1 billion principal amount of 5.00 percent senior notes due 2033 (the “2033 Senior Notes”) and $500 million principal amount of 5.65 percent senior notes due 2053 (the “2053 Senior Notes”). The 2033 Senior Notes were offered at a price to the public of 99.170 percent of par with interest payable semi-annually in arrears, commencing on September 1, 2023. The 2053 Senior Notes were offered at a price to the public of 99.536 percent of par with interest payable semi-annually in arrears, commencing on September 1, 2023.

Revenue

Revenue	3 Months Ended
	Mar. 31, 2023
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, 2023 and March 31, 2022: 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 Three Months Ended March 31, 2022 (In millions) L&S G&P Total Revenues and other income: Service revenue $ 72 $ 482 $ 554 Service revenue - related parties 911 4 915 Service revenue - product related — 123 123 Product sales 1 496 497 Product sales - related parties 3 42 45 Total revenues from contracts with customers $ 987 $ 1,147 2,134 Non-ASC 606 revenue (1) 476 Total revenues and other income $ 2,610 (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. These balances are included in Receivables, net on the Consolidated Balance Sheets. 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-month periods ended March 31, 2023 and March 31, 2022: (In millions) Balance at December 31, 2022 Additions/ (Deletions) Revenue Recognized (1) Balance at 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) $ — $ — (In millions) Balance at December 31, 2021 Additions/ (Deletions) Revenue Recognized (1) Balance at Contract assets $ 25 $ (18) $ — $ 7 Long-term contract assets 2 — — 2 Deferred revenue 56 11 (9) 58 Deferred revenue - related parties 60 34 (26) 68 Long-term deferred revenue 135 2 — 137 Long-term deferred revenue - related parties 31 — — 31 Long-term contract liabilities $ 5 $ — $ — $ 5 (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) at the end of the reporting period. As of March 31, 2023, unsatisfied performance obligations included in the Consolidated Balance Sheets are $370 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 below as it is deemed variable consideration due to volume variability. Additionally, we do not disclose information on the future performance obligations for any contract with an original expected duration of one year or less. (In millions) 2023 $ 1,346 2024 1,680 2025 1,589 2026 1,433 2027 1,312 2028 and thereafter 708 Total revenue on remaining performance obligations (1)(2)(3) $ 8,068 (1) All fixed consideration from contracts with customers is included in the amounts presented above. Variable consideration that is constrained or not required to be estimated as it reflects our efforts to perform is excluded. (2) Revenues classified as Rental income and Sales-type lease revenue are excluded from this table.

Supplemental Cash Flow Informat

Supplemental Cash Flow Information	3 Months Ended
	Mar. 31, 2023
Supplemental Cash Flow Elements [Abstract]
Supplemental Cash Flow Information	Supplemental Cash Flow Information Three Months Ended (In millions) 2023 2022 Net cash provided by operating activities included: Interest paid (net of amounts capitalized) $ 270 $ 213 Income taxes paid 1 — Non-cash investing and financing activities: Net transfers of property, plant and equipment (to)/from materials and supplies inventories 9 — Net transfers of property, plant and equipment to lease receivable $ 28 $ 10 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) 2023 2022 Additions to property, plant and equipment $ 169 $ 169 Increase in capital accruals 22 3 Total capital expenditures $ 191 $ 172

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2023
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 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 (together, 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 seek disgorgement of pipeline profits from June 1, 2013 to present, removal of the pipeline and remediation. We intend to vigorously defend ourselves against these counterclaims. 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 a joint venture that owns and operates the Dakota Access Pipeline and Energy Transfer Crude Oil Pipeline projects, collectively referred to as the Bakken Pipeline system or DAPL. In 2020, the U.S. District Court for the District of Columbia (the “D.D.C.”) ordered the U.S. 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 EIS has been delayed and the Army Corps currently expects to release a draft EIS in 2023. In May 2021, the D.D.C. denied a renewed request for an injunction to shut down the pipeline while the EIS is being prepared. In June 2021, the D.D.C. issued an order dismissing without prejudice the tribes’ claims against the Dakota Access Pipeline. The litigation could be reopened or new litigation challenging the EIS, once completed, could be filed. The pipeline remains operational. 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 pipeline were temporarily shut down, 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 permit and/or return the pipeline into operation. If the vacatur of the easement permit 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, 2023, 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, 2023, 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.

Description of the Business a_2

Description of the Business and Basis of Presentation Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2023
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 7 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, 2023
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.

Investments and Noncontrollin_2

Investments and Noncontrolling Interests (Tables)	3 Months Ended
	Mar. 31, 2023
Equity Method Investments and Joint Ventures [Abstract]
Equity Method Investments	The following table presents MPLX’s equity method investments at the dates indicated: Ownership as of Carrying value at March 31, March 31, December 31, (In millions, except ownership percentages) VIE 2023 2023 2022 L&S Andeavor Logistics Rio Pipeline LLC X 67% $ 176 $ 177 Illinois Extension Pipeline Company, L.L.C. 35% 243 236 LOOP LLC 41% 292 287 MarEn Bakken Company LLC (1) 25% 466 475 Minnesota Pipe Line Company, LLC 17% 177 178 Whistler Pipeline LLC 38% 217 211 Other (2) X 289 269 Total L&S 1,860 1,833 G&P Centrahoma Processing LLC 40% 129 131 MarkWest EMG Jefferson Dry Gas Gathering Company, L.L.C X 67% 336 335 MarkWest Torñado GP, L.L.C. X 60% 312 306 MarkWest Utica EMG, L.L.C. X 58% 692 669 Rendezvous Gas Services, L.L.C. X 78% 135 137 Sherwood Midstream Holdings LLC X 51% 122 125 Sherwood Midstream LLC X 50% 509 512 Other (2) X 49 47 Total G&P 2,284 2,262 Total $ 4,144 $ 4,095 (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 or DAPL. (2) Some investments included within Other have also been deemed to be VIEs.

Related Party Agreements and _2

Related Party Agreements and Transactions (Tables)	3 Months Ended
	Mar. 31, 2023
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 $ 559 $ 610 Lease receivables 121 111 Prepaid 17 5 Other 4 3 Total 701 729 Noncurrent assets - related parties Long-term lease receivables 865 883 Right of use assets 228 228 Unguaranteed residual asset 95 87 Long-term receivables 24 27 Total 1,212 1,225 Current liabilities - related parties MPC loan agreement and other payables (1) 239 262 Deferred revenue 87 80 Operating lease liabilities 1 1 Total 327 343 Long-term liabilities - related parties Long-term operating lease liabilities 227 228 Long-term deferred revenue 111 110 Total $ 338 $ 338 (1) There were no borrowings outstanding on the MPC Loan Agreement as of March 31, 2023 or December 31, 2022.

Equity (Tables)

Equity (Tables)	3 Months Ended
	Mar. 31, 2023
Equity [Abstract]
Schedule of Stockholders Equity	The changes in the number of common units during the three months ended March 31, 2023 are summarized below: (In units) Common Units Balance at December 31, 2022 1,001,020,616 Unit-based compensation awards 142,742 Balance at March 31, 2023 1,001,163,358
Distributions Made to Limited Partner, by Distribution	The allocation of total quarterly cash distributions to limited and preferred unitholders is as follows for the three months ended March 31, 2023 and March 31, 2022. 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) 2023 2022 Common and preferred unit distributions: Common unitholders, includes common units of general partner $ 776 $ 713 Series A preferred unit distributions 23 21 Series B preferred unit distributions (1) 5 11 Total cash distributions declared $ 804 $ 745 (1) Represents the portion of the $21 million distribution paid to the Series B preferred unitholders on February 15, 2023 that was earned during the three months ended March 31, 2023.

Net Income Per Limited Partne_3

Net Income Per Limited Partner Unit (Tables)	3 Months Ended
	Mar. 31, 2023
Earnings Per Share [Abstract]
Schedule of Distributions By Partner By Class	During the three months ended March 31, 2023 and March 31, 2022, MPLX had participating securities consisting of common units, certain equity-based compensation awards, Series A preferred units and Series B preferred units and 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, 2023 and March 31, 2022 were less than 1 million. Three Months Ended (In millions) 2023 2022 Net income attributable to MPLX LP $ 943 $ 825 Less: Distributions declared on Series A preferred units 23 21 Distributions declared on Series B preferred units 5 11 Limited partners’ distributions declared on MPLX common units (including common units of general partner) 776 713 Undistributed net gain attributable to MPLX LP $ 139 $ 80
Schedule of Net Income Per Unit, Basic and Diluted	Three Months Ended March 31, 2023 (In millions, except per unit data) Limited Partners’ Series A Preferred Units Series B Preferred Units Total Basic and diluted net income attributable to MPLX LP per unit Net income attributable to MPLX LP: Distributions declared $ 776 $ 23 $ 5 $ 804 Undistributed net gain attributable to MPLX LP 135 4 — 139 Net income attributable to MPLX LP (1) 911 $ 27 $ 5 943 Impact of redemption of Series B preferred units (5) (5) Income available to common unitholders $ 906 $ 938 Weighted average units outstanding: Basic 1,001 Diluted 1,001 Net income attributable to MPLX LP per limited partner unit: Basic $ 0.91 Diluted $ 0.91 (1) Allocation of net income attributable to MPLX LP assumes all earnings for the period had been distributed based on the distribution priorities applicable to the period. Three Months Ended March 31, 2022 (In millions, except per unit data) Limited Partners’ Series A Preferred Units Series B Preferred Units Total Basic and diluted net income attributable to MPLX LP per unit Net income attributable to MPLX LP: Distributions declared $ 713 $ 21 $ 11 $ 745 Undistributed net gain attributable to MPLX LP 78 2 — 80 Net income attributable to MPLX LP (1) $ 791 $ 23 $ 11 $ 825 Weighted average units outstanding: Basic 1,015 Diluted 1,015 Net income attributable to MPLX LP per limited partner unit: Basic $ 0.78 Diluted $ 0.78 (1) Allocation of net income attributable to MPLX LP assumes all earnings for the period had been distributed based on the distribution priorities applicable to the period.

Segment Information (Tables)

Segment Information (Tables)	3 Months Ended
	Mar. 31, 2023
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) 2023 2022 L&S Service revenue $ 1,033 $ 983 Rental income 212 175 Product related revenue 5 4 Sales-type lease revenue 125 111 Income from equity method investments 71 52 Other income 14 12 Total segment revenues and other income (1) 1,460 1,337 Segment Adjusted EBITDA (2) 1,026 904 Capital expenditures 68 77 Investments in unconsolidated affiliates 15 68 G&P Service revenue 525 486 Rental income 51 81 Product related revenue 564 661 Sales-type lease revenue 34 — Income from equity method investments 63 47 Other income (loss) 16 (2) Total segment revenues and other income (1) 1,253 1,273 Segment Adjusted EBITDA (2) 493 489 Capital expenditures 123 95 Investments in unconsolidated affiliates $ 36 $ 42 (1) Within the total segment revenues and other income amounts presented above, third party revenues for the L&S segment were $170 million and $135 million for the three months ended March 31, 2023 and March 31, 2022, respectively. Third party revenues for the G&P segment were $1,166 million and $1,212 million for the three months ended March 31, 2023 and March 31, 2022, respectively. (2) See below for the reconciliation from Segment Adjusted EBITDA to Net income.
Reconciliation of Other Significant Reconciling Items from Segments to Consolidated	The table below provides a reconciliation between Net income and Segment Adjusted EBITDA. Three Months Ended (In millions) 2023 2022 Reconciliation to Net income: L&S Segment Adjusted EBITDA $ 1,026 $ 904 G&P Segment Adjusted EBITDA 493 489 Total reportable segments 1,519 1,393 Depreciation and amortization (1) (296) (313) Interest and other financial costs (243) (222) Income from equity method investments 134 99 Distributions/adjustments related to equity method investments (153) (132) Adjusted EBITDA attributable to noncontrolling interests 10 9 Other (2) (19) (1) Net income $ 952 $ 833 (1) Depreciation and amortization attributable to L&S was $129 million and $130 million for the three months ended March 31, 2023 and March 31, 2022 , respectively. Depreciation and amortization attributable to G&P was $167 million and $183 million for the three months ended March 31, 2023 and March 31, 2022, respectively.

Property, Plant and Equipment (

Property, Plant and Equipment (Tables)	3 Months Ended
	Mar. 31, 2023
Property, Plant and Equipment [Abstract]
Summary of Property, Plant and Equipment	Property, plant and equipment with associated accumulated depreciation is shown below: March 31, 2023 December 31, 2022 (In millions) Gross PP&E Accumulated Depreciation Net PP&E Gross PP&E Accumulated Depreciation Net PP&E L&S $ 12,476 $ 3,673 $ 8,803 $ 12,416 $ 3,554 $ 8,862 G&P 13,607 3,652 9,955 13,495 3,509 9,986 Total $ 26,083 $ 7,325 $ 18,758 $ 25,911 $ 7,063 $ 18,848

Fair Value Measurements (Tables

Fair Value Measurements (Tables)	3 Months Ended
	Mar. 31, 2023
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, 2023 and December 31, 2022 by fair value hierarchy level. March 31, 2023 December 31, 2022 (In millions) Asset Liability Asset Liability Commodity contracts (Level 2) Other current assets / Other current liabilities $ 2 $ — $ — $ — Embedded derivatives in commodity contracts (Level 3) Other current assets / Other current liabilities — 11 — 10 Other noncurrent assets / Other long-term liabilities — 47 — 51 Total carrying value in Consolidated Balance Sheets $ 2 $ 58 $ — $ 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) 2023 2022 Beginning balance $ (61) $ (108) Unrealized and realized gain included in Net Income (1) — 4 Settlements 3 5 Ending balance $ (58) $ (99) The amount of total gain/(loss) for the period included in earnings attributable to the change in unrealized gain/(loss) relating to liabilities still held at end of period $ — $ 5 (1) Gain/(loss) 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, 2023 December 31, 2022 (In millions) Fair Value Carrying Value Fair Value Carrying Value Outstanding debt (1) $ 19,167 $ 20,517 $ 18,095 $ 19,905 (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, 2023
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Schedule of Notional Amounts of Outstanding Derivative Positions	As of March 31, 2023, MPLX had the following outstanding commodity contracts that were executed to manage the price risk associated with sales of propane during 2023: Derivative contracts not designated as hedging instruments Financial Position Notional Quantity Propane (gal) Short 33,970,000
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) 2023 2022 Product sales: Unrealized gain $ 2 $ — Product sales derivative gain 2 — Purchased product costs: Realized loss (3) (5) Unrealized gain 3 9 Purchased product cost derivative gain — 4 Total derivative gain included in Net income $ 2 $ 4

Debt (Tables)

Debt (Tables)	3 Months Ended
	Mar. 31, 2023
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 20,046 Consolidated subsidiaries: MarkWest 12 23 ANDX 31 31 Financing lease obligations 7 8 Total 20,707 20,108 Unamortized debt issuance costs (130) (117) Unamortized discount (183) (195) Amounts due within one year (1) (988) Total long-term debt due after one year $ 20,393 $ 18,808

Revenue (Tables)

Revenue (Tables)	3 Months Ended
	Mar. 31, 2023
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, 2023 and March 31, 2022: 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 Three Months Ended March 31, 2022 (In millions) L&S G&P Total Revenues and other income: Service revenue $ 72 $ 482 $ 554 Service revenue - related parties 911 4 915 Service revenue - product related — 123 123 Product sales 1 496 497 Product sales - related parties 3 42 45 Total revenues from contracts with customers $ 987 $ 1,147 2,134 Non-ASC 606 revenue (1) 476 Total revenues and other income $ 2,610
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-month periods ended March 31, 2023 and March 31, 2022: (In millions) Balance at December 31, 2022 Additions/ (Deletions) Revenue Recognized (1) Balance at 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) $ — $ — (In millions) Balance at December 31, 2021 Additions/ (Deletions) Revenue Recognized (1) Balance at Contract assets $ 25 $ (18) $ — $ 7 Long-term contract assets 2 — — 2 Deferred revenue 56 11 (9) 58 Deferred revenue - related parties 60 34 (26) 68 Long-term deferred revenue 135 2 — 137 Long-term deferred revenue - related parties 31 — — 31 Long-term contract liabilities $ 5 $ — $ — $ 5
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) at the end of the reporting period. As of March 31, 2023, unsatisfied performance obligations included in the Consolidated Balance Sheets are $370 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 below as it is deemed variable consideration due to volume variability. Additionally, we do not disclose information on the future performance obligations for any contract with an original expected duration of one year or less. (In millions) 2023 $ 1,346 2024 1,680 2025 1,589 2026 1,433 2027 1,312 2028 and thereafter 708 Total revenue on remaining performance obligations (1)(2)(3) $ 8,068 (1) All fixed consideration from contracts with customers is included in the amounts presented above. Variable consideration that is constrained or not required to be estimated as it reflects our efforts to perform is excluded. (2) Revenues classified as Rental income and Sales-type lease revenue are excluded from this table.

Supplemental Cash Flow Inform_2

Supplemental Cash Flow Information (Tables)	3 Months Ended
	Mar. 31, 2023
Supplemental Cash Flow Elements [Abstract]
Schedule of Cash Flow, Supplemental Disclosures	Three Months Ended (In millions) 2023 2022 Net cash provided by operating activities included: Interest paid (net of amounts capitalized) $ 270 $ 213 Income taxes paid 1 — Non-cash investing and financing activities: Net transfers of property, plant and equipment (to)/from materials and supplies inventories 9 — Net transfers of property, plant and equipment to lease receivable $ 28 $ 10
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) 2023 2022 Additions to property, plant and equipment $ 169 $ 169 Increase in capital accruals 22 3 Total capital expenditures $ 191 $ 172

Description of Business and Bas

Description of Business and Basis of Presentation - Additional Information (Detail)	3 Months Ended
	Mar. 31, 2023
Accounting Policies [Abstract]
Number of reportable segments	2

Investments and Noncontrollin_3

Investments and Noncontrolling Interests (Summary of Equity Method Investment Financial Information) (Details) - USD ($) $ in Millions		Mar. 31, 2023	Dec. 31, 2022
Schedule of Equity Method Investments
Equity method investments		$ 4,144	$ 4,095
Indirect Ownership Interest [Member] | Sherwood Midstream Holdings LLC
Schedule of Equity Method Investments
Equity method investment, ownership percentage		24.54%
L&S
Schedule of Equity Method Investments
Equity method investments		$ 1,860	1,833
L&S | Andeavor Logistics Rio Pipeline LLC
Schedule of Equity Method Investments
Equity method investment, ownership percentage		67%
Equity method investments	[1]	$ 176	177
L&S | Illinois Extension Pipeline Company, L.L.C.
Schedule of Equity Method Investments
Equity method investment, ownership percentage		35%
Equity method investments		$ 243	236
L&S | LOOP LLC
Schedule of Equity Method Investments
Equity method investment, ownership percentage		41%
Equity method investments		$ 292	287
L&S | MarEn Bakken Company LLC(1)
Schedule of Equity Method Investments
Equity method investment, ownership percentage		25%
Equity method investments	[2]	$ 466	475
L&S | Minnesota Pipe Line Company, LLC
Schedule of Equity Method Investments
Equity method investment, ownership percentage		17%
Equity method investments		$ 177	178
L&S | Whistler Pipeline LLC
Schedule of Equity Method Investments
Equity method investment, ownership percentage		38%
Equity method investments		$ 217	211
L&S | Other VIEs and Non-VIEs
Schedule of Equity Method Investments
Equity method investments	[1]	$ 289	269
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		$ 2,284	2,262
G&P | Centrahoma Processing LLC
Schedule of Equity Method Investments
Equity method investment, ownership percentage		40%
Equity method investments		$ 129	131
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	[1]	$ 336	335
G&P | MarkWest Torñado GP, L.L.C.
Schedule of Equity Method Investments
Equity method investment, ownership percentage		60%
Equity method investments	[1]	$ 312	306
G&P | MarkWest Utica EMG, L.L.C.
Schedule of Equity Method Investments
Equity method investment, ownership percentage		58%
Equity method investments	[1]	$ 692	669
G&P | Rendezvous Gas Services, L.L.C.
Schedule of Equity Method Investments
Equity method investment, ownership percentage		78%
Equity method investments	[1]	$ 135	137
G&P | Sherwood Midstream Holdings LLC
Schedule of Equity Method Investments
Equity method investments	[1]	$ 122	125
G&P | Sherwood Midstream LLC
Schedule of Equity Method Investments
Equity method investment, ownership percentage		50%
Equity method investments	[1]	$ 509	512
G&P | Other VIEs and Non-VIEs
Schedule of Equity Method Investments
Equity method investments	[1]	$ 49	$ 47
G&P | Direct Ownership Interest [Member] | Sherwood Midstream Holdings LLC
Schedule of Equity Method Investments
Equity method investment, ownership percentage		51%
[1]Some investments included within Other have also been deemed to be VIEs.[2]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 or DAPL.

Related Party Loan (Details)

Related Party Loan (Details) - Revolving Credit Facility - Related Party [Member] - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Dec. 31, 2022
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, 2023	Mar. 31, 2022
Related Party [Member]
Related Party Transaction [Line Items]
Sales Revenue, Goods, Related Party, Net Zero	$ 198	$ 293

Related Party Expenses (Details

Related Party Expenses (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Related Party Transaction [Line Items]
General and administrative expenses	$ 89	$ 78
Related Party [Member]
Related Party Transaction [Line Items]
General and administrative expenses	64	55
Asset under Construction [Member] | Related Party [Member]
Related Party Transaction [Line Items]
Property, Plant and Equipment, Additions	$ 10	$ 19

Related Party Assest and Liabil

Related Party Assest and Liabilities (Details) - USD ($) $ in Millions		Mar. 31, 2023	Dec. 31, 2022
Related Party Transaction [Line Items]
Receivables, net		$ 714	$ 737
Other current assets		63	53
Accounts payable		139	224
Operating lease liabilities		45	46
Long-term operating lease liabilities		221	230
Long-term deferred revenue		233	219
Related Party [Member]
Related Party Transaction [Line Items]
Receivables, net		559	610
Lease receivables		121	111
Prepaid		17	5
Other current assets		4	3
Current assets - related parties		701	729
Long-term lease receivables		865	883
Right of use assets, net		228	228
Unguaranteed residual asset		95	87
Long-term receivables		24	27
Noncurrent assets - related parties		1,212	1,225
Accounts payable	[1]	239	262
Deferred revenue		87	80
Operating lease liabilities		1	1
Other current liabilities		327	343
Long-term operating lease liabilities		227	228
Long-term deferred revenue		111	110
Other Liabilities, Noncurrent		338	338
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, 2023 or December 31, 2022.

Other Related Party Transaction

Other Related Party Transactions (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Related Party Transaction [Line Items]
Revenues	$ 2,713	$ 2,610
Asset and Inventory transfers | Related Party [Member]
Related Party Transaction [Line Items]
Revenues	$ 5	$ 8

Equity - Changes in Partners Ca

Equity - Changes in Partners Capital, Unit Rollforward (Details)	3 Months Ended
	Mar. 31, 2023 shares
Stockholders Equity [Line Items]
Balance at December 31, 2022	1,001,020,616
Unit-based compensation awards	142,742
Balance at March 31, 2023	1,001,163,358

Repurchase Program (Details)

Repurchase Program (Details) - USD ($) $ in Millions	Mar. 31, 2023	Aug. 02, 2022
Equity, Class of Treasury Stock [Line Items]
Stock Repurchase Program, Authorized Amount		$ 1,000
Stock Repurchase Program, Remaining Authorized Repurchase Amount	$ 846

Series B Redemption (Details)

Series B Redemption (Details) - USD ($) $ / shares in Units, $ in Millions		3 Months Ended
	Feb. 15, 2023	Mar. 31, 2023	Mar. 31, 2022
Equity, Class of Treasury Stock [Line Items]
Partners' Capital Account, Distributions		$ 808	$ 746
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

Equity - Cash Distributions (De

Equity - Cash Distributions (Details) - USD ($) $ / shares in Units, $ in Millions					3 Months Ended
	May 15, 2023	May 05, 2023	Apr. 25, 2023	Feb. 15, 2023	Mar. 31, 2023	Mar. 31, 2022
Distribution Made to Limited Partner [Line Items]
Distribution Made to Limited Partner, Cash Distributions Declared					$ 804	$ 745
Cash distributions declared per limited partner common unit					$ 0.775	$ 0.705
Series A Preferred Stock [Member]
Distribution Made to Limited Partner [Line Items]
Distribution Made to Limited Partner, Cash Distributions Declared					$ 23	$ 21
Series B Preferred Stock [Member]
Distribution Made to Limited Partner [Line Items]
Distribution Made to Limited Partner, Cash Distributions Declared					5	11
Distribution date				Feb. 15, 2023
Common Stock [Member]
Distribution Made to Limited Partner [Line Items]
Distribution Made to Limited Partner, Cash Distributions Declared					$ 776	$ 713
Subsequent Event
Distribution Made to Limited Partner [Line Items]
Distribution Made to Limited Partner, Cash Distributions Declared			$ 776
Distribution Made to Limited Partner, Declaration Date			Apr. 25, 2023
Cash distributions declared per limited partner common unit			$ 0.775
Date of record		May 05, 2023
Subsequent Event | Common Stock [Member]
Distribution Made to Limited Partner [Line Items]
Distribution date	May 15, 2023

Net Income Per Limited Partne_4

Net Income Per Limited Partner Unit - Schedule of Distributions by Partner by Class (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2023	Mar. 31, 2022
Net Income Per Share [Line Items]
Net income attributable to MPLX LP	[1]	$ 943	$ 825
Distribution Made to Limited Partner, Cash Distributions Declared		804	745
Undistributed net gain attributable to MPLX LP		139	80
Series A Preferred Stock [Member]
Net Income Per Share [Line Items]
Net income attributable to MPLX LP	[1]	27	23
Distribution Made to Limited Partner, Cash Distributions Declared		23	21
Undistributed net gain attributable to MPLX LP		4	2
Series B Preferred Stock [Member]
Net Income Per Share [Line Items]
Net income attributable to MPLX LP	[1]	5	11
Distribution Made to Limited Partner, Cash Distributions Declared		5	11
Undistributed net gain attributable to MPLX LP		0	0
Common Stock [Member]
Net Income Per Share [Line Items]
Net income attributable to MPLX LP	[1]	911	791
Distribution Made to Limited Partner, Cash Distributions Declared		776	713
Undistributed net gain attributable to MPLX LP		$ 135	$ 78
[1]Allocation of net income attributable to MPLX LP assumes all earnings for the period had been distributed based on the distribution priorities applicable to the period.

Net Income Per Limited Partne_5

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, 2023	Mar. 31, 2022
Schedule Of Earnings Per Share Basic And Diluted [Line Items]
Distribution Made to Limited Partner, Cash Distributions Declared		$ 804	$ 745
Undistributed net gain attributable to MPLX LP		139	80
Net income attributable to MPLX LP	[1]	943	$ 825
Impact of redemption of Series B preferred units		(5)
Net Income (Loss) Available to Common Stockholders, Basic		$ 938
Antidilutive Securities Excluded from Computation of Earnings Per Share, Amount		1	1
Weighted average units outstanding:
Common - basic		1,001	1,015
Common - diluted		1,001	1,015
Net income attributable to MPLX LP per limited partner unit:
Common - basic		$ 0.91	$ 0.78
Common - diluted		$ 0.91	$ 0.78
Series A Preferred Stock [Member]
Schedule Of Earnings Per Share Basic And Diluted [Line Items]
Distribution Made to Limited Partner, Cash Distributions Declared		$ 23	$ 21
Undistributed net gain attributable to MPLX LP		4	2
Net income attributable to MPLX LP	[1]	27	23
Series B Preferred Stock [Member]
Schedule Of Earnings Per Share Basic And Diluted [Line Items]
Distribution Made to Limited Partner, Cash Distributions Declared		5	11
Undistributed net gain attributable to MPLX LP		0	0
Net income attributable to MPLX LP	[1]	5	11
Common Stock [Member]
Schedule Of Earnings Per Share Basic And Diluted [Line Items]
Distribution Made to Limited Partner, Cash Distributions Declared		776	713
Undistributed net gain attributable to MPLX LP		135	78
Net income attributable to MPLX LP	[1]	911	$ 791
Impact of redemption of Series B preferred units		(5)
Net Income (Loss) Available to Common Stockholders, Basic		$ 906
[1]Allocation of net income attributable to MPLX LP assumes all earnings for the period had been distributed based on the distribution priorities applicable to the period.

Segment Information (Details)

Segment Information (Details)	3 Months Ended
	Mar. 31, 2023
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, 2023	Mar. 31, 2022
Segment Reporting Information [Line Items]
Sales-type lease revenue - related parties		$ 125	$ 111
Sales-type lease revenue		34	0
Income from equity method investments		134	99
Revenues		2,713	2,610
Capital Expenditure		191	172
Investments in unconsolidated affiliates		51	110
L&S
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		1,038	987
G&P
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		1,089	1,147
Operating Segments
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		2,127	2,134
Adjusted EBITDA		1,519	1,393
Operating Segments | L&S
Segment Reporting Information [Line Items]
Rental income		212	175
Sales-type lease revenue		125	111
Income from equity method investments		71	52
Other income		14	12
Revenues	[1]	1,460	1,337
Adjusted EBITDA	[2]	1,026	904
Capital Expenditure		68	77
Investments in unconsolidated affiliates		15	68
Operating Segments | G&P
Segment Reporting Information [Line Items]
Rental income		51	81
Sales-type lease revenue		34	0
Income from equity method investments		63	47
Other income		16	(2)
Revenues	[1]	1,253	1,273
Adjusted EBITDA	[2]	493	489
Capital Expenditure		123	95
Investments in unconsolidated affiliates		36	42
Service [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		605	554
Service [Member] | L&S
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		83	72
Service [Member] | G&P
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		522	482
Service [Member] | Operating Segments | L&S
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		1,033	983
Service [Member] | Operating Segments | G&P
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		525	486
Product [Member]
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		420	497
Product [Member] | L&S
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		2	1
Product [Member] | G&P
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		418	496
Product [Member] | Operating Segments | L&S
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		5	4
Product [Member] | Operating Segments | G&P
Segment Reporting Information [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		564	661
Third Party [Member] | L&S
Segment Reporting Information [Line Items]
Revenues		170	135
Third Party [Member] | G&P
Segment Reporting Information [Line Items]
Revenues		$ 1,166	$ 1,212
[1]Within the total segment revenues and other income amounts presented above, third party revenues for the L&S segment were $170 million and $135 million for the three months ended March 31, 2023 and March 31, 2022, respectively. Third party revenues for the G&P segment were $1,166 million and $1,212 million for the three months ended March 31, 2023 and March 31, 2022, respectively.[2]See below for the reconciliation from Segment Adjusted EBITDA to Net income.

Segment Information - Reconcili

Segment Information - Reconciliation to Net Income (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2023	Mar. 31, 2022
Segment Reporting, Revenue Reconciling Item [Line Items]
Depreciation and amortization(1)	[1]	$ (296)	$ (313)
Income from equity method investments		134	99
Proceeds from Equity Method Investment, Distribution		(140)	(120)
Net income		952	833
Operating Segments
Segment Reporting, Revenue Reconciling Item [Line Items]
Adjusted EBITDA		1,519	1,393
Segment Reconciling Items [Member]
Segment Reporting, Revenue Reconciling Item [Line Items]
Interest and Other Financial Costs		(243)	(222)
Proceeds from Equity Method Investment, Distribution		(153)	(132)
Adjusted EBITDA attributable to noncontrolling interests		10	9
Other Cost and Expense, Operating		(19)	(1)
L&S
Segment Reporting, Revenue Reconciling Item [Line Items]
Depreciation and amortization(1)		(129)	(130)
L&S | Operating Segments
Segment Reporting, Revenue Reconciling Item [Line Items]
Adjusted EBITDA	[2]	1,026	904
Income from equity method investments		71	52
G&P
Segment Reporting, Revenue Reconciling Item [Line Items]
Depreciation and amortization(1)		(167)	(183)
G&P | Operating Segments
Segment Reporting, Revenue Reconciling Item [Line Items]
Adjusted EBITDA	[2]	493	489
Income from equity method investments		$ 63	$ 47
[1]Depreciation and amortization attributable to L&S was $129 million and $130 million for the three months ended March 31, 2023 and March 31, 2022 , respectively. Depreciation and amortization attributable to G&P was $167 million and $183 million for the three months ended March 31, 2023 and March 31, 2022, respectively.(2)    Includes unrealized derivative gain/(loss), non-cash equity-based compensation, provision for income taxes, and other miscellaneous items.[2]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	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022	Dec. 31, 2022
Property, Plant and Equipment [Line Items]
Capitalized interest	$ 3	$ 2
Gross PP&E	26,083		$ 25,911
Accumulated Depreciation	7,325		7,063
Property, Plant, and Equipment and Finance Lease Right-of-Use Asset, after Accumulated Depreciation and Amortization, Total	18,758		18,848
L&S
Property, Plant and Equipment [Line Items]
Gross PP&E	12,476		12,416
Accumulated Depreciation	3,673		3,554
Property, Plant, and Equipment and Finance Lease Right-of-Use Asset, after Accumulated Depreciation and Amortization, Total	8,803		8,862
G&P
Property, Plant and Equipment [Line Items]
Gross PP&E	13,607		13,495
Accumulated Depreciation	3,652		3,509
Property, Plant, and Equipment and Finance Lease Right-of-Use Asset, after Accumulated Depreciation and Amortization, Total	$ 9,955		$ 9,986

Fair Values - Recurring - Balan

Fair Values - Recurring - Balance Sheet Location Table (Details) - USD ($) $ in Millions	Mar. 31, 2023	Dec. 31, 2022
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset, Subject to Master Netting Arrangement, before Offset	$ 2	$ 0
Derivative Liability, Subject to Master Netting Arrangement, before Offset	58	61
Fair Value, Inputs, Level 2 [Member] | Commodity Contract [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	2	0
Fair Value, Inputs, Level 2 [Member] | Commodity Contract [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	0	0
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	11	10
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	$ 47	$ 51

Fair Values - Recurring - Signi

Fair Values - Recurring - Significant Unobservable Inputs in Level 3 Valuation (Details)	3 Months Ended
	Mar. 31, 2023 USD ($) $ / gal
Fair Value Inputs, Assets and Liabilities, Quantitative Information [Line Items]
Derivative, Average Forward Price | $ / gal	0.77
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	0.58
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	1.55

Changes in Level 3 Fair Value M

Changes in Level 3 Fair Value Measurements (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2023	Mar. 31, 2022
Fair Value, Liabilities Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Beginning balance		$ (61)	$ (108)
Unrealized and realized gain included in Net Income(1)	[1]	0	4
Settlements		3	5
Ending balance		$ (58)	$ (99)
[1]Gain/(loss) 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, 2023	Mar. 31, 2022
Fair Value Disclosures [Abstract]
The amount of total gain/(loss) for the period included in earnings attributable to the change in unrealized gain/(loss) relating to liabilities still held at end of period	$ 0	$ 5

Fair Values - Reported (Details

Fair Values - Reported (Details) - USD ($) $ in Millions		Mar. 31, 2023	Dec. 31, 2022
Estimate of Fair Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-Term Debt, Fair Value	[1]	$ 19,167	$ 18,095
Reported Value Measurement [Member]
Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items]
Long-Term Debt, Fair Value	[1]	$ 20,517	$ 19,905
[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.

Schedule of Outstanding Derivat

Schedule of Outstanding Derivative Positions (Details)	Mar. 31, 2023 gal
Propane | Short | Over-the-Counter
Derivative [Line Items]
Derivative, Nonmonetary Notional Amount, Volume	33,970,000

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, 2023 USD ($)	Dec. 31, 2022 USD ($)
Fair Value, Inputs, Level 3 [Member] | Fair Value, Recurring [Member]
Derivative [Line Items]
Derivative Liability	$ (58)	$ (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, 2023	Dec. 31, 2022
Derivatives, Fair Value [Line Items]
Derivative Liability, Subject to Master Netting Arrangement, before Offset	$ 58	$ 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	11	10
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	$ 47	$ 51

Derivatives Financial Instrumen

Derivatives Financial Instruments - Derivative Income Statement Location (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Derivative [Line Items]
Derivative, Gain (Loss) on Derivative, Net	$ 2	$ 4
Derivative, Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Net income	Net income
Purchased product costs
Derivative [Line Items]
Realized gain (loss)	$ (3)	$ (5)
Unrealized Gain (Loss) on Derivatives and Commodity Contracts	3	9
Derivative, Gain (Loss) on Derivative, Net	0	4
Product Sales
Derivative [Line Items]
Unrealized Gain (Loss) on Derivatives and Commodity Contracts	2	0
Derivative, Gain (Loss) on Derivative, Net	$ 2	$ 0

Debt - Summary of Outstanding B

Debt - Summary of Outstanding Borrowings (Detail) - USD ($) $ in Millions	Mar. 31, 2023	Dec. 31, 2022
Debt Instrument [Line Items]
MPLX Credit Agreement	$ 0	$ 0
Financing lease obligations	7	8
Debt and Lease Obligation	20,707	20,108
Unamortized debt issuance costs	(130)	(117)
Unamortized discount	(183)	(195)
Amounts due within one year	1	988
Total long-term debt due after one year	20,393	18,808
MPLX LP [Member]
Debt Instrument [Line Items]
Senior Notes	20,657	20,046
MarkWest [Member]
Debt Instrument [Line Items]
Senior Notes	12	23
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, 2023	Dec. 31, 2022
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) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022	Mar. 13, 2023	Feb. 09, 2023
Series B Preferred Stock [Member]
Debt Instrument [Line Items]
Payments for Repurchase of Preferred Stock and Preference Stock	$ 600	$ 0
Senior Notes [Member] | Senior Notes Due March 2033 and March 2053
Debt Instrument [Line Items]
Debt Instrument, Face Amount				$ 1,600
Senior Notes [Member] | Senior Note Due March 2033
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage				5%
Debt Instrument, Face Amount				$ 1,100
Percent of Par				99.17%
Senior Notes [Member] | Senior Note Due March 2053
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage				5.65%
Debt Instrument, Face Amount				$ 500
Percent of Par				99.536%
Senior Notes [Member] | Senior Notes Due July 2023
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage			4.50%
Gain (Loss) on Extinguishment of Debt	9
Repayments of Debt	$ 1,000
Minimum [Member] | Senior Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	1.75%
Maximum [Member] | Senior Notes [Member]
Debt Instrument [Line Items]
Debt Instrument, Interest Rate, Stated Percentage	5.65%

Revenue Disaggregation of Reven

Revenue Disaggregation of Revenue (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2023	Mar. 31, 2022
Disaggregation of Revenue [Line Items]
Revenue Not from Contract with Customer, Other	[1]	$ 586	$ 476
Revenues		2,713	2,610
Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		2,127	2,134
L&S
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		1,038	987
L&S | Operating Segments
Disaggregation of Revenue [Line Items]
Revenues	[2]	1,460	1,337
G&P
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		1,089	1,147
G&P | Operating Segments
Disaggregation of Revenue [Line Items]
Revenues	[2]	1,253	1,273
Service [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		605	554
Revenue from Contract with Customer, Excluding Assessed Tax, Related Parties		953	915
Service [Member] | L&S
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		83	72
Revenue from Contract with Customer, Excluding Assessed Tax, Related Parties		950	911
Service [Member] | L&S | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		1,033	983
Service [Member] | G&P
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		522	482
Revenue from Contract with Customer, Excluding Assessed Tax, Related Parties		3	4
Service [Member] | G&P | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		525	486
Service, Other [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		79	123
Service, Other [Member] | L&S
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		0	0
Service, Other [Member] | G&P
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		79	123
Product [Member]
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		420	497
Revenue from Contract with Customer, Excluding Assessed Tax, Related Parties		70	45
Product [Member] | L&S
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		2	1
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	4
Product [Member] | G&P
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		418	496
Revenue from Contract with Customer, Excluding Assessed Tax, Related Parties		67	42
Product [Member] | G&P | Operating Segments
Disaggregation of Revenue [Line Items]
Revenue from Contract with Customer, Excluding Assessed Tax		$ 564	$ 661
[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 $170 million and $135 million for the three months ended March 31, 2023 and March 31, 2022, respectively. Third party revenues for the G&P segment were $1,166 million and $1,212 million for the three months ended March 31, 2023 and March 31, 2022, respectively.

Revenue Contract Balances (Deta

Revenue Contract Balances (Details) - USD ($) $ in Millions		3 Months Ended
		Mar. 31, 2023	Mar. 31, 2022	Dec. 31, 2022	Dec. 31, 2021
Contract with Customer, Asset, before Allowance for Credit Loss		$ 16	$ 7	$ 21	$ 25
Contract assets, additions/(deletions)		(5)	(18)
Contract with Customer, Asset, Reclassified to Receivable	[1]	0	0
Contract with Customer, Asset, before Allowance for Credit Loss, Noncurrent		0	2	1	2
Contract with Customer, Asset Increase (Decrease), Noncurrent		(1)	0
Contract With Customer Non Current Asset Reclassified To Receivable [Line Items]	[1]	0	0
Contract Liability, Current, Revenue Recognized		0
Contract Liability, Current, Period Increase (Decrease)		1
Contract with Customer, Liability, Current		1		0
Long-term deferred revenue		233		219
Contract with Customer, Liability, Noncurrent		0	5	2	5
Contract Liability, Noncurrent, Period Increase (Decrease)		(2)	0
Contract Liability, Noncurrent, Revenue Recognized	[1]	0	0
Liability, change in timeframe, performance obligation satisfied, revenue recognized		0	0
Nonrelated Party [Member]
Deferred revenue		45	58	57	56
Deferred revenue, revenue recognized	[1]	(14)	(9)
Deferred Revenue, Additions		2	11
Long-term deferred revenue		231	137	216	135
Long-term deferred revenue, additions/(deletions)		15	2
Long-term deferred revenue, revenue recognized	[1]	0	0
Related Party [Member]
Deferred revenue		87		80
Deferred revenue, revenue recognized	[1]	(26)	(26)
Deferred Revenue, Additions		32	34
Deferred Revenue from Contracts with Customers, Current		69	68	63	60
Long-term deferred revenue		111		110
Long-term deferred revenue, additions/(deletions)		1	0
Long-term deferred revenue, revenue recognized	[1]	0	0
Deferred Revenue from Contracts with Customers, Noncurrent		$ 26	$ 31	$ 25	$ 31
[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, 2023 USD ($)
Revenue from Contract with Customer [Abstract]
Contract with customer, liability	$ 370
Revenue, Remaining Performance Obligation, Amount	8,068	[1],[2],[3]
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-04-01
Revenue from Contract with Customer [Abstract]
Revenue, Remaining Performance Obligation, Amount	$ 1,346
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation, expected timing of satisfaction, years	9 months
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2024-01-01
Revenue from Contract with Customer [Abstract]
Revenue, Remaining Performance Obligation, Amount	$ 1,680
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation, expected timing of satisfaction, years	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2025-01-01
Revenue from Contract with Customer [Abstract]
Revenue, Remaining Performance Obligation, Amount	$ 1,589
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation, expected timing of satisfaction, years	2 years
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2026-01-01
Revenue from Contract with Customer [Abstract]
Revenue, Remaining Performance Obligation, Amount	$ 1,433
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation, expected timing of satisfaction, years	3 years
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2027-01-01
Revenue from Contract with Customer [Abstract]
Revenue, Remaining Performance Obligation, Amount	$ 1,312
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation, expected timing of satisfaction, years	4 years
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2028-01-01
Revenue from Contract with Customer [Abstract]
Revenue, Remaining Performance Obligation, Amount	$ 708
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation, expected timing of satisfaction, years	5 years
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2043-10-01
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction [Line Items]
Remaining performance obligation, expected timing of satisfaction, years	21 years
[1]All fixed consideration from contracts with customers is included in the amounts presented above. Variable consideration that is constrained or not required to be estimated as it reflects our efforts to perform is excluded.[2]Only minimum volume commitments that are deemed fixed are included in the table above. MPLX has various minimum volume commitments in processing arrangements that vary based on the actual Btu content of the gas received. These amounts are deemed variable consideration and are excluded from the table above.[3]Revenues classified as Rental income and Sales-type lease revenue are excluded from this table.

Supplemental Cash Flow Inform_3

Supplemental Cash Flow Information - Summary of Supplemental Cash Flow Information (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Other Significant Noncash Transactions [Line Items]
Interest paid (net of amounts capitalized)	$ 270	$ 213
Income taxes paid	1	0
Net transfers of property, plant and equipment (to)/from materials and supplies inventories	9	0
Reclassification, Other
Other Significant Noncash Transactions [Line Items]
Property, Plant and Equipment, Transfers and Changes	$ 28	$ 10

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, 2023	Mar. 31, 2022
Supplemental Cash Flow Elements [Abstract]
Additions to property, plant and equipment	$ 169	$ 169
Increase in capital accruals	22	3
Capital Expenditure	$ 191	$ 172

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, 2023	Dec. 31, 2022
Commitments And Contingencies [Line Items]
Accrued liabilities for environmental remediation			$ 17	$ 17
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 a joint venture that owns and operates the Dakota Access Pipeline and Energy Transfer Crude Oil Pipeline projects, collectively referred to as the Bakken Pipeline system or DAPL. In 2020, the U.S. District Court for the District of Columbia (the “D.D.C.”) ordered the U.S. 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 EIS has been delayed and the Army Corps currently expects to release a draft EIS in 2023.In May 2021, the D.D.C. denied a renewed request for an injunction to shut down the pipeline while the EIS is being prepared. In June 2021, the D.D.C. issued an order dismissing without prejudice the tribes’ claims against the Dakota Access Pipeline. The litigation could be reopened or new litigation challenging the EIS, once completed, could be filed. The pipeline remains operational.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 pipeline were temporarily shut down, 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 permit and/or return the pipeline into operation. If the vacatur of the easement permit 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, 2023, our maximum potential undiscounted payments under the Contingent Equity Contribution Agreement were approximately $170 million.
Environmental Loss Contingency, Statement of Financial Position [Extensible Enumeration]			Other long-term liabilities, Other current liabilities	Other long-term liabilities, Other current liabilities
Financial Guarantee [Member] | Bakken Pipeline System [Member] | Guarantee of Indebtedness of Others [Member]
Commitments And Contingencies [Line Items]
Guarantor Obligations, Maximum Exposure, Undiscounted			$ 170