Acquisitions and Investments (Schedule of Acquisition Related Pro Forma Financial Information) (Details) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended	9 Months Ended
Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Business Combinations [Abstract]
Sales and other operating revenues (including consumer excise taxes)	$ 28,284	$ 29,317	$ 84,232	$ 86,386
Net income attributable to MPC	$ 698	$ 170	$ 1,748	$ 1,516
Net income attributable to MPC per share - basic	$ 2.48	$ 0.55	$ 6.07	$ 4.72
Net income attributable to MPC per share - diluted	$ 2.46	$ 0.55	$ 6.03	$ 4.69

The pro forma basic net income per share for a period as if the business combination or combinations had been completed at the beginning of a period.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 805

-SubTopic 10

-Section 50

-Paragraph 2

-Subparagraph (h)(2)-(3)

-URI http://asc.fasb.org/extlink&oid=25497992&loc=d3e1392-128463

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The pro forma diluted net income per share for a period as if the business combination or combinations had been completed at the beginning of a period.

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The pro forma net Income or Loss for the period as if the business combination or combinations had been completed at the beginning of a period.

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The pro forma revenue for a period as if the business combination or combinations had been completed at the beginning of the period.

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