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Share capital
6 Months Ended
Jun. 30, 2011
Share capital [Abstract]  
Share capital
7. Share capital
The following table reflects changes in the number of shares of Class A Stock outstanding for the periods indicated:
                                 
    Three months ended     Six months ended  
    June 30,     June 30,  
    2011     2010     2011     2010  
Class A Stock outstanding, beginning of period
    13,535,063       13,241,552       13,268,522       13,118,001  
Issued pursuant to the share-based compensation plans
    33,882       11,470       300,423       135,021  
 
                       
Class A Stock outstanding, end of period
    13,568,945       13,253,022       13,568,945       13,253,022