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Earnings Per Share
 12 Months Ended
Dec. 31, 2011
Earnings Per Share [Abstract]  
Earnings Per Share
3. Earnings Per Share

Basic and diluted earnings per share are calculated as follows:

 

     Years Ended December 31  
     2011      2010      2009  

Basic earnings per share

         

Numerator:

         

Net income

    $ 206,907       $ 177,125       $ 162,283   
  

 

 

     

 

 

     

 

 

  

Denominator:

         

Weighted-average number of shares of common stock outstanding

      13,707         14,619         15,206   
  

 

 

     

 

 

     

 

 

  

Basic earnings per share

    $ 15.10       $ 12.12       $ 10.67   
  

 

 

     

 

 

     

 

 

  

Diluted earnings per share

         

Numerator:

         

Net income

    $ 206,907       $ 177,125       $ 162,283   
  

 

 

     

 

 

     

 

 

  

Denominator:

         

Weighted-average number of shares of common stock outstanding

      13,707         14,619         15,206   

Shares issuable upon exercise of stock options

      5         31         37   
  

 

 

     

 

 

     

 

 

  

Total shares

      13,712         14,650         15,243   
  

 

 

     

 

 

     

 

 

  

Diluted earnings per share

    $ 15.09       $ 12.09       $ 10.65   
  

 

 

     

 

 

     

 

 

  

Options are not included in the computation of diluted earnings per share when the option exercise price exceeds the average market price of the underlying common share, as the impact on earnings per share would be anti-dilutive. We had no anti-dilutive options that were excluded from the calculation of earnings per share for any period presented.