Income per Common Share (Tables)

12 Months Ended

Dec. 31, 2018

Earnings Per Share [Abstract]

Summary of Earnings Per Common Share

Since MPC grants certain incentive compensation awards to employees and non-employee directors that are considered to be participating securities, we have calculated our earnings per share using the two-class method. Diluted income per share assumes exercise of certain stock-based compensation awards, provided the effect is not anti-dilutive.

(In millions, except per share data)	2018		2017		2016
Basic earnings per share:
Allocation of earnings:
Net income attributable to MPC	$	2,780	$	3,432	$	1,174
Income allocated to participating securities	1		2		1
Income available to common stockholders – basic	$	2,779	$	3,430	$	1,173
Weighted average common shares outstanding	518		507		528
Basic earnings per share	$	5.36	$	6.76	$	2.22
Diluted earnings per share:
Allocation of earnings:
Net income attributable to MPC	$	2,780	$	3,432	$	1,174
Income allocated to participating securities	1		2		1
Income available to common stockholders – diluted	$	2,779	$	3,430	$	1,173
Weighted average common shares outstanding	518		507		528
Effect of dilutive securities	8		5		2
Weighted average common shares, including dilutive effect	526		512		530
Diluted earnings per share	$	5.28	$	6.70	$	2.21

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.

(In millions)	2018	2017	2016
Shares issuable under stock-based compensation plans	—	1	3