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STOCK-BASED COMPENSATION
 6 Months Ended
Jun. 30, 2014
STOCK-BASED COMPENSATION  
STOCK-BASED COMPENSATION

12. STOCK-BASED COMPENSATION

We grant various types of share-based payment awards to participants, including restricted stock unit awards and stock option grants. The key terms of our restricted stock unit awards and our stock option grants, including all financial disclosures, are set forth in our Annual Report on Form 10-K for the year ended December 31, 2013.

Information regarding our stock-based compensation expense for the three and six month periods ended June 30, 2014 are as follows:

 
   Three Months Ended June 30,   Six Months Ended June 30,  
(In millions)
  2014   2013   2014   2013  

Stock based compensation expense

     $ 4.3     $ 2.6     $ 7.1     $ 4.5  

Income tax provision related to stock compensation expense

     (1.5 )   (0.9 )   (2.5 )   (1.5 )
                   
​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

After tax share based compensation expense

     $ 2.8     $ 1.7     $ 4.6     $ 3.0  
                   
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​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​
                   

In computing diluted earnings per share for the three and six months ended June 30, 2014, common stock equivalents of 0.6 million and 0.3 million shares were not included due to their anti-dilutive effect. For both the three and six months ended June 30, 2013, common stock equivalents of 0.1 million shares were not included due to their anti-dilutive effect. Certain of our restricted stock units participate in dividend distributions, however, the distributions for these restricted stock units do not have a material impact on our earnings per share calculation.