Equity Method Investments (Watson Cogeneration Company) (Details) $ in Millions		12 Months Ended
	Jun. 01, 2022 USD ($)	Dec. 31, 2022 USD ($)		Dec. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)
Schedule of Equity Method Investments [Line Items]
Payments to acquire businesses, net of cash acquired		$ 413		$ 0	$ 0
Book value of equity method investment		150	[1]	0	0
Net gain on disposal of assets		$ 1,061		$ 21	$ 70
Watson Cogeneration Company
Schedule of Equity Method Investments [Line Items]
Equity method investment, remaining ownership interest purchased	0.49
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] Represents the book value of MPC’s equity method investment in Watson Cogeneration Company and Crowley Ocean Partners prior to MPC buying out the remaining interest in these entities. See Note 16 for additional information