Earnings Per Common Share
 6 Months Ended
Jun. 30, 2017
Earnings Per Share [Abstract]  
Earnings Per Common Share
Earnings Per Share
The effect of dilutive securities on the weighted average common shares outstanding included in the calculation of earnings per diluted common share for the three and six months ended June 30, 2017 and 2016 were as follows:
 
Three Months Ended
June 30
 
Six Months Ended
June 30
(number of shares in millions)
2017
 
2016
 
2017
 
2016
Weighted average common shares outstanding
257.1

 
267.2

 
257.4

 
267.4

Effect of dilutive securities:
 
 
 
 
 
 
 
Stock options
1.1

 
0.9

 
1.1

 
0.9

Other stock compensation awards
0.8

 
1.0

 
0.8

 
0.9

Potentially dilutive common shares
1.9

 
1.9

 
1.9

 
1.8

Adjusted weighted average common shares outstanding
259.0

 
269.1

 
259.3

 
269.2


Excluded from the computation of earnings per diluted share due to their antidilutive effect were 0.6 million outstanding stock options for the three and six months ended June 30, 2017 and 2016.