Income per Common Share (Tables)

9 Months Ended

Sep. 30, 2014

Earnings Per Share [Abstract]

Summary of Earnings Per Common Share

	Three Months Ended   September 30,				Nine Months Ended   September 30,
(In millions, except per share data)	2014		2013		2014		2013
Basic earnings per share:
Allocation of earnings:
Net income attributable to MPC	$	672	$	168	$	1,726	$	1,486
Income allocated to participating securities	1		—		3		2
Income available to common stockholders - basic	$	671	$	168	$	1,723	$	1,484
Weighted average common shares outstanding	282		309		288		321
Basic earnings per share	$	2.38	$	0.54	$	5.99	$	4.63
Diluted earnings per share:
Allocation of earnings:
Net income attributable to MPC	$	672	$	168	$	1,726	$	1,486
Income allocated to participating securities	1		—		3		2
Income available to common stockholders - diluted	$	671	$	168	$	1,723	$	1,484
Weighted average common shares outstanding	282		309		288		321
Effect of dilutive securities	2		2		2		2
Weighted average common shares, including dilutive effect	284		311		290		323
Diluted earnings per share	$	2.36	$	0.54	$	5.95	$	4.60

Schedule of Antidilutive Securities Excluded from Computation of Earnings Per Share

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

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