Debt (Available Capacity under our Facilities) (Details) - USD ($) $ in Millions		Dec. 31, 2024	Jul. 31, 2022	Jul. 07, 2022
MPC bank revolving credit facility due July 2027
Line of Credit Facility [Line Items]
Total Capacity		$ 5,000
Outstanding Borrowings		0
Outstanding Letters of Credit		1
Available Capacity		$ 4,999
Weighted Average Interest Rate		0.00%
Trade Receivables Securitization due September 2027
Line of Credit Facility [Line Items]
Total Capacity		$ 100
Outstanding Borrowings		0
Outstanding Letters of Credit		0
Available Capacity	[1]	$ 100
Weighted Average Interest Rate		0.00%
Line of credit facility, maximum borrowing capacity		$ 100	$ 100
MPLX revolving credit facility due July 2027
Line of Credit Facility [Line Items]
Available Capacity		2,000
MPLX revolving credit facility due July 2027 | MPLX
Line of Credit Facility [Line Items]
Total Capacity		2,000
Outstanding Borrowings		0
Outstanding Letters of Credit		$ 0
Weighted Average Interest Rate		0.00%
Line of credit facility, maximum borrowing capacity				$ 2,000

[1] The committed borrowing and letter of credit issuance capacity under the trade receivables securitization facility is $100 million. In addition, the facility allows for the issuance of letters of credit in excess of the committed capacity at the discretion of the issuing banks.