Income per Common Share

6 Months Ended

Jun. 30, 2014

Earnings Per Share [Abstract]

Income per Common Share

Income per Common Share

We compute basic earnings per share by dividing net income attributable to MPC by the weighted average number of shares of common stock outstanding. Diluted income per share assumes exercise of certain stock-based compensation awards, provided the effect is not anti-dilutive.

MPC grants certain incentive compensation awards to employees and non-employee directors that are considered to be participating securities. Due to the presence of participating securities, we have calculated our earnings per share using the two-class method.

	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

The following table summarizes the shares that were anti-dilutive and, therefore, were excluded from the diluted share calculation.

	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