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Earnings per common share
9 Months Ended
Sep. 30, 2011
Earnings per common share [Abstract] 
Earnings per common share
 5.
Earnings per common share
 
Basic earnings per common share were computed by dividing earnings on common stock by the weighted average number of shares of common stock outstanding during the applicable period. Diluted earnings per common share were computed by dividing earnings on common stock by the total of the weighted average number of shares of common stock outstanding during the applicable period, plus the effect of outstanding stock options and performance share awards. For the three and nine months ended September 30, 2011 and 2010, there were no shares excluded from the calculation of diluted earnings per share. Common stock outstanding includes issued shares less shares held in treasury.