Debt (MPLX Bank Revolving Credit Facility) (Details) $ in Millions	Jul. 07, 2022 USD ($) Period	Dec. 31, 2022 USD ($)
MPC bank revolving credit facility due July 2027
Debt Instrument [Line Items]
Total capacity		$ 5,000
MPLX | MPLX revolving credit facility due July 2024
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	$ 3,500
MPLX | MPLX revolving credit facility due July 2027
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	$ 2,000
Total capacity		$ 2,000
Debt instrument, description of variable rate basis	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
Number of renewal periods | Period	2
MPLX | MPLX revolving credit facility due July 2027 | Maximum
Debt Instrument [Line Items]
Line of credit facility additional borrowing capacity	$ 1,000
Number of prior quarterly reporting periods covenant	4
Covenant ratio debt to EBITDA	5.0
Covenant ratio debt to EBITDA post acquisition	5.5
MPLX | MPLX revolving credit facility due July 2027 | Letter of Credit | Maximum
Debt Instrument [Line Items]
Total capacity	$ 150
Marathon Petroleum Corporation | MPC bank revolving credit facility due July 2027
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity	$ 5,000
Debt instrument, description of variable rate basis	at either the Adjusted Term SOFR or the Alternate Base Rate, both as defined in the MPC Credit Agreement, plus an applicable margin
Number of renewal periods | Period	2
Marathon Petroleum Corporation | MPC bank revolving credit facility due July 2027 | Maximum
Debt Instrument [Line Items]
Line of credit facility additional borrowing capacity	$ 1,000
Marathon Petroleum Corporation | MPC bank revolving credit facility due July 2027 | Letter of Credit
Debt Instrument [Line Items]
Total capacity	2,200
Marathon Petroleum Corporation | MPC bank revolving credit facility due July 2027 | Letter of Credit | Maximum
Debt Instrument [Line Items]
Total capacity	$ 3,000