Earnings Per Share (Summary of Earnings Per Share) (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Earnings Per Share [Abstract]
Net income	$ 1,015	$ 3,631	$ 4,282	$ 9,295
Net income attributable to noncontrolling interest	(393)	(351)	(1,208)	(1,065)
Net income allocated to participating securities	0	(2)	(2)	(5)
Redemption of preferred units	0	0	0	(2)
Income available to common stockholders	$ 622	$ 3,278	$ 3,072	$ 8,223
Weighted average common shares outstanding:
Basic (in shares)	331	394	347	418
Effect of dilutive securities (in shares)	1	2	1	2
Diluted (in shares)	332	396	348	420
Basic:
Net income attributable to MPC per share	$ 1.88	$ 8.31	$ 8.85	$ 19.66
Diluted:
Net income attributable to MPC per share	$ 1.87	$ 8.28	$ 8.83	$ 19.57