Equity Method Investments (Watson Cogeneration Company) (Details) - USD ($) $ in Millions		12 Months Ended
	Jun. 01, 2022	Dec. 31, 2024	Dec. 31, 2023		Dec. 31, 2022
Schedule of Equity Method Investments [Line Items]
Payments to acquire businesses, net of cash acquired		$ 688	$ 246		$ 413
Book value of equity method investment		50	311	[1]	150
Net gain on disposal of assets		$ 28	$ 217		$ 1,061
Watson Cogeneration Company
Schedule of Equity Method Investments [Line Items]
Equity method investment, remaining ownership interest purchased	49.00%
Payments to acquire businesses, net of cash acquired	$ 59
Fair value of assets contributed	62
Book value of equity method investment	$ 25
Equity method investments, ownership percentage	51.00%
Net gain on disposal of assets	$ 37

[1] 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.