Income per Common Share (Tables)

6 Months Ended

Jun. 30, 2014

Earnings Per Share [Abstract]

Summary of Earnings Per Common Share

	Three Months Ended   June 30,				Six Months Ended   June 30,
(In millions, except per share data)	2014		2013		2014		2013
Basic earnings per share:
Allocation of earnings:
Net income attributable to MPC	$	855	$	593	$	1,054	$	1,318
Income allocated to participating securities	1		1		2		2
Income available to common stockholders - basic	$	854	$	592	$	1,052	$	1,316
Weighted average common shares outstanding	287		322		290		326
Basic earnings per share	$	2.97	$	1.84	$	3.63	$	4.03
Diluted earnings per share:
Allocation of earnings:
Net income attributable to MPC	$	855	$	593	$	1,054	$	1,318
Income allocated to participating securities	1		1		2		2
Income available to common stockholders - diluted	$	854	$	592	$	1,052	$	1,316
Weighted average common shares outstanding	287		322		290		326
Effect of dilutive securities	2		2		2		2
Weighted average common shares, including dilutive effect	289		324		292		328
Diluted earnings per share	$	2.95	$	1.83	$	3.60	$	4.01

Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share

	Three Months Ended   June 30,		Six Months Ended   June 30,
(In millions)	2014	2013	2014	2013
Shares issued under stock-based compensation plans	—	1	—	1