Supplemental Cash Flow Information (Summary Of Supplemental Cash Flow Information) (Details) - USD ($) $ in Millions				12 Months Ended
	Oct. 01, 2024	Dec. 01, 2022	Jun. 01, 2022	Dec. 31, 2024		Dec. 31, 2023		Dec. 31, 2022	Sep. 30, 2024
Net cash provided by operating activities included:
Interest paid (net of amounts capitalized)				$ 1,247		$ 1,200		$ 1,060
Income taxes paid to taxing authorities				732	[1]	2,751		4,869
Payments on operating leases				532		493		498
Interest payments under finance lease obligations				25		25		24
Net cash provided by financing activities included:
Principal payments under finance lease obligations				82		79		79
Non-cash investing and financing activities:
Right of use assets obtained in exchange for new operating lease obligations				637		465		367
Right of use assets obtained in exchange for new finance lease obligations				302		21		60
Contribution of net assets				0		0	[2]	818
Book value of equity method investment				50		$ 311	[3]	$ 150
Income Tax Credits and Adjustments				$ 565
Coastal Holdings
Non-cash investing and financing activities:
Book value of equity method investment	$ 50
Equity method investments, ownership percentage									50.00%
Watson Cogeneration Company
Non-cash investing and financing activities:
Book value of equity method investment			$ 25
Equity method investments, ownership percentage			51.00%
Tanker Holdings
Non-cash investing and financing activities:
Book value of equity method investment		$ 125
Equity method investments, ownership percentage						50.00%

[1] 2024 includes $565 million paid to third parties for transferable tax credits.

[2] Represents the book value of property, plant and equipment, inventory and working capital contributed by MPC to Martinez Renewables LLC. See Note 14 for additional information.

[3] 2024 represents the book value of Coastal Holdings prior to MPC buying out the remaining 50 percent interest from our joint venture partner. 2023 represents the book value of MPLX’s equity method investment in Torñado, prior to MPLX buying out the remaining interest in this entity. 2022 represents the book value of MPC’s equity method investment in Watson Cogeneration Company and Tanker Holdings of $25 million and $125 million, respectively, prior to MPC buying out the remaining interest in these entities. See Note 14 for additional information.