v3.24.3
Debt - Summary of Outstanding Borrowings (Detail) - USD ($)
$ in Millions
May 20, 2024
Sep. 30, 2024
Dec. 31, 2023
Debt Instrument [Line Items]      
MPLX Credit Agreement   $ 0 $ 0
Finance lease obligations   6 6
Debt and Lease Obligation   22,356 20,706
Unamortized debt issuance costs   (129) (122)
Unamortized discount   (141) (153)
Amounts due within one year   2,836 1,135
Total long-term debt due after one year   19,250 19,296
Senior Note Due June 2034 [Domain] | Senior Notes [Member]      
Debt Instrument [Line Items]      
Debt Instrument, Face Amount $ 1,650    
Debt Instrument, Interest Rate, Stated Percentage 5.50%    
Percent of Par 98.778%    
Debt Instrument, Issuance Date May 20, 2024    
MPLX LP [Member]      
Debt Instrument [Line Items]      
Senior Notes   22,307 20,657
MPLX LP [Member] | Senior Notes Due December 2024 | Senior Notes [Member]      
Debt Instrument [Line Items]      
Debt Instrument, Face Amount   $ 1,149  
Debt Instrument, Interest Rate, Stated Percentage   4.875%  
MPLX LP [Member] | Senior Notes Due February 2025 | Senior Notes [Member]      
Debt Instrument [Line Items]      
Debt Instrument, Face Amount   $ 500  
Debt Instrument, Interest Rate, Stated Percentage   4.00%  
MarkWest [Member]      
Debt Instrument [Line Items]      
Senior Notes   $ 12 12
MarkWest [Member] | Senior Notes Due December 2024 | Senior Notes [Member]      
Debt Instrument [Line Items]      
Debt Instrument, Face Amount   $ 1  
Debt Instrument, Interest Rate, Stated Percentage   4.875%  
ANDX LP [Member]      
Debt Instrument [Line Items]      
Senior Notes   $ 31 $ 31