Equity Method Investments	9 Months Ended
Equity Method Investments	Sep. 30, 2024
Equity Method Investments and Joint Ventures [Abstract]
Equity Method Investments	Equity Method Investments BANGL, LLC Acquisition On July 31, 2024, MPLX exercised its right of first offer under the BANGL, LLC joint venture agreement to purchase an additional 20 percent ownership interest in BANGL, LLC for $210 million cash, increasing total ownership interest to 45 percent (the “BANGL Transaction”). BANGL is a natural gas liquids pipeline system connecting the Delaware and Midland basins to the fractionation market in Sweeny, Texas. The purchase price of the additional 20 percent ownership interest in BANGL, LLC exceeded our portion of the underlying net assets of the joint venture by approximately $156 million.This basis difference is being amortized into net income over the remaining estimated useful lives of the underlying net assets. Following the BANGL Transaction, our investment in BANGL, LLC continues to be accounted for as an equity method investment. Whistler Joint Venture Transaction On May 29, 2024, MPLX and its joint venture partner contributed their respective membership interest in Whistler Pipeline, LLC to a newly formed joint venture, WPC Parent, LLC, and issued a 19 percent voting interest in WPC Parent, LLC to an affiliate of Enbridge Inc. in exchange for the contribution of cash and the Rio Bravo Pipeline project (collectively the “Whistler Joint Venture Transaction”). As a result of the transaction, MPLX’s voting interest in the joint venture was reduced from 37.5 percent to 30.4 percent. MPLX recognized a gain of $151 million at closing and received a cash distribution of $134 million, recorded as a return of capital, related to the dilution of the ownership interest. The gain is included in income from equity method investments on the accompanying consolidated statements of income and the return of capital is included in investments - redemptions, repayments, return of capital and sales proceeds within the investing section of the accompanying consolidated statements of cash flows. Midstream Acquisition On March 22, 2024, MPLX used $625 million of cash on hand to purchase additional ownership interest in existing joint ventures and gathering assets, which will enhance MPLX’s position in the Utica basin. Prior to the acquisition, MPLX owned an indirect interest in Ohio Gathering Company, L.L.C. (“OGC”) and a direct interest in Ohio Condensate Company, L.L.C. (“OCC”) and now owns a combined 73 percent interest in OGC and a 100 percent interest in OCC, and a dry gas gathering system in the Utica basin. OGC continues to be accounted for as an equity method investment as MPLX did not obtain control of OGC as a result of the transaction. OGC is considered a VIE and MPLX is not deemed to be the primary beneficiary due to voting rights on significant matters. The acquisition date fair value of our investment in OGC exceeded our portion of the underlying net assets of the joint venture by approximately $86 million. This basis difference is being amortized into net income over the remaining estimated useful lives of the underlying net assets. OCC was previously accounted for as an equity method investment, and it is now consolidated and included in our consolidated financial results. The acquisition was accounted for as a business combination requiring all the acquired assets and liabilities to be remeasured to fair value resulting in a consolidated fair value of net assets and liabilities of $625 million. The fair value includes $518 million related to acquired interests in the joint ventures and the remaining balance related to other acquired assets and liabilities. The revaluation of MPLX’s existing 62 percent equity method investment in OCC resulted in a $20 million gain, which is included in net gain on disposal of assets on the accompanying consolidated statements of income. The fair value of equity method investments was based on a discounted cash flow model. South Texas Gateway Terminal LLC On August 1, 2023, MPC sold its 25 percent interest in South Texas Gateway Terminal LLC (“South Texas Gateway”) to an affiliate of Gibson Energy Inc. (“Gibson Energy”). Gibson Energy paid $1.1 billion in cash to acquire 100 percent of the membership interests of South Texas Gateway from MPC and its other members. South Texas Gateway owns an oil export facility in the U.S. Gulf Coast. MPC’s proceeds were $270 million, resulting in a gain of $106 million, which is included in net gain on disposal of assets on the accompanying consolidated statements of income. LF Bioenergy Acquisition On March 8, 2023, MPC announced the acquisition of a 49.9 percent interest in LF Bioenergy, an emerging producer of renewable natural gas (“RNG”) in the U.S., for approximately $56 million, which included funding for on-going operations and project development. LF Bioenergy has been focused on developing and growing a portfolio of dairy farm-based, low carbon intensity RNG projects. LF Bioenergy is a VIE since it is unable to fund its operations without financial support from its equity owners. We are not the primary beneficiary of this VIE because we do not have the ability to control the activities that significantly influence the economic outcomes of the entity and, therefore, do not consolidate the entity. MPC accounts for our ownership interest in LF Bioenergy as an equity method investment.