v3.26.1
Document and Entity Information - shares
3 Months Ended
Mar. 31, 2026
Apr. 30, 2026
Cover [Abstract]    
Document Fiscal Year Focus 2026  
Document Fiscal Period Focus Q1  
Entity Central Index Key 0001552000  
Current Fiscal Year End Date --12-31  
Amendment Flag false  
Document Type 10-Q  
Document Quarterly Report true  
Document Period End Date Mar. 31, 2026  
Document Transition Report false  
Entity File Number 001-35714  
Entity Registrant Name MPLX LP  
Entity Incorporation, State or Country Code DE  
Entity Tax Identification Number 27-0005456  
Entity Address, Address Line One 200 E. Hardin Street,  
Entity Address, City or Town Findlay,  
Entity Address, State or Province OH  
Entity Address, Postal Zip Code 45840  
City Area Code 419  
Local Phone Number 422-2121  
Title of 12(b) Security Common Units Representing Limited Partnership Interests  
Trading Symbol MPLX  
Security Exchange Name NYSE  
Entity Current Reporting Status Yes  
Entity Interactive Data Current Yes  
Entity Filer Category Large Accelerated Filer  
Entity Small Business false  
Entity Emerging Growth Company false  
Entity Shell Company false  
Entity Partnership, Units Outstanding   1,014,733,719