Acquisitions and Investments (Schedule of Acquisition Related Pro Forma Financial Information (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2015	Dec. 31, 2014
Business Combinations [Abstract]
Sales and other operating revenues (including consumer excise taxes)	$ 73,760	$ 108,605
Net income attributable to MPC	$ 2,825	$ 2,522
Net income attributable to MPC per share – basic	$ 5.25	$ 4.42
Net income attributable to MPC per share – diluted	$ 5.21	$ 4.39