v3.26.1
Investments and Noncontrolling Interests (Schedule of Equity Method Investments) (Details) - USD ($)
$ in Millions
6 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Dec. 31, 2025
Jun. 16, 2025
Schedule of Equity Method Investments        
Equity method investments $ 5,149   $ 4,798  
Equity Method Investments, Including Held for Sale 5,149   4,798  
Investments - redemptions, repayments, return of capital and sales proceeds $ 0 $ 60    
MXP Parent, LLC        
Schedule of Equity Method Investments        
Equity method investment, ownership percentage       10.00%
Indirect Ownership Interest [Member] | Bakken Pipeline System [Member]        
Schedule of Equity Method Investments        
Equity method investment, ownership percentage 9.19%      
Crude Oil and Products Logistics        
Schedule of Equity Method Investments        
Equity method investments $ 1,574   1,581  
Crude Oil and Products Logistics | Illinois Extension Pipeline Company, L.L.C.        
Schedule of Equity Method Investments        
Equity method investment, ownership percentage 35.00%      
Equity method investments $ 220   208  
Crude Oil and Products Logistics | LOOP LLC        
Schedule of Equity Method Investments        
Equity method investment, ownership percentage 41.00%      
Equity method investments $ 304   313  
Crude Oil and Products Logistics | MarEn Bakken Company LLC(1)        
Schedule of Equity Method Investments        
Equity method investment, ownership percentage 25.00%      
Equity method investments [1] $ 492   502  
Crude Oil and Products Logistics | Other VIEs and Non-VIEs        
Schedule of Equity Method Investments        
Equity method investments [2] $ 558   558  
Crude Oil and Products Logistics | Other VIEs and Non-VIEs | Minimum [Member]        
Schedule of Equity Method Investments        
Equity method investment, ownership percentage 17.00%      
Crude Oil and Products Logistics | Other VIEs and Non-VIEs | Maximum [Member]        
Schedule of Equity Method Investments        
Equity method investment, ownership percentage 67.00%      
Natural Gas and NGL Services        
Schedule of Equity Method Investments        
Equity method investments $ 3,575   3,217  
Natural Gas and NGL Services | MarkWest EMG Jefferson Dry Gas Gathering Company, L.L.C.        
Schedule of Equity Method Investments        
Equity method investment, ownership percentage 67.00%      
Equity method investments $ 396   407  
Natural Gas and NGL Services | MarkWest Utica EMG, L.L.C.        
Schedule of Equity Method Investments        
Equity method investment, ownership percentage 62.00%      
Equity method investments $ 957   890  
Natural Gas and NGL Services | Ohio Gathering Company L.L.C.        
Schedule of Equity Method Investments        
Equity method investment, ownership percentage 31.00%      
Equity method investments [3] $ 425   444  
Natural Gas and NGL Services | Sherwood Midstream LLC        
Schedule of Equity Method Investments        
Equity method investment, ownership percentage 50.00%      
Equity method investments $ 468   475  
Natural Gas and NGL Services | WPC Parent, LLC        
Schedule of Equity Method Investments        
Equity method investment, ownership percentage 30.00%      
Equity method investments $ 272   273  
Natural Gas and NGL Services | Other VIEs and Non-VIEs        
Schedule of Equity Method Investments        
Equity method investments [2] $ 499   367  
Natural Gas and NGL Services | Other VIEs and Non-VIEs | Minimum [Member]        
Schedule of Equity Method Investments        
Equity method investment, ownership percentage 10.00%      
Natural Gas and NGL Services | Other VIEs and Non-VIEs | Maximum [Member]        
Schedule of Equity Method Investments        
Equity method investment, ownership percentage 51.00%      
Natural Gas and NGL Services | Texas City Logistics LLC        
Schedule of Equity Method Investments        
Equity method investment, ownership percentage 50.00%      
Equity method investments $ 316   163  
Natural Gas and NGL Services | MXP Parent, LLC        
Schedule of Equity Method Investments        
Equity method investment, ownership percentage 10.00%      
Equity method investments $ 242   $ 198  
Natural Gas and NGL Services | Indirect Ownership Interest [Member] | Ohio Gathering Company L.L.C.        
Schedule of Equity Method Investments        
Equity method investment, ownership percentage 43.00%      
[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, the “Bakken Pipeline system”).
[2] Included within Other are certain equity method investments that have been deemed to be VIEs.
[3] MPLX also holds a 43 percent indirect interest in Ohio Gathering Company L.L.C. through our ownership interest in MarkWest Utica EMG, L.L.C.