XML 87 R73.htm IDEA: XBRL DOCUMENT v3.7.0.1
Income Per Common Share - Summary of Earnings Per Common Share (Detail) - USD ($)
$ / shares in Units, shares in Millions, $ in Millions
 3 Months Ended
Mar. 31, 2017
Mar. 31, 2016
Basic earnings per share:    
Net income attributable to MPC $ 30 $ 1
Income allocated to participating securities 0 0
Income available to common stockholders – basic $ 30 $ 1
Weighted average common shares outstanding (in shares) 525 529
Basic (in USD per share) $ 0.06 $ 0.003
Diluted earnings per share:    
Net income attributable to MPC $ 30 $ 1
Income allocated to participating securities 0 0
Income available to common stockholders – diluted $ 30 $ 1
Weighted average common shares outstanding (in shares) 525 529
Effect of dilutive securities (in shares) 5 2
Weighted average common shares, including dilutive effect (in shares) 530 531
Diluted (in USD per share) $ 0.06 $ 0.003