Earnings per Share
9 Months Ended
Sep. 30, 2011
Earnings Per Share [Abstract] 
Earnings per Share
15.  Earnings per Share:

The Company calculates earnings per share using the two-class method.  The two-class method requires allocating the Company's net earnings to both common shares and participating securities.  The following table sets forth the computation of basic and diluted earnings per common share (in millions, except for share and per-share data):

   
Three months ended
September 30,
  
Nine months ended
September 30,
 
   
2011
  
2010
  
2011
  
2010
 
Numerator:
            
Net earnings
 $34.6  $19.3  $105.1  $89.5 
Less: net earnings allocated to participating securities (a)
  (0.5)  (0.3)  (1.7)  (1.6)
Net earnings available to common shareholders
 $34.1  $19.0  $103.4  $87.9 
Denominator (in thousands):
                
Weighted-average common shares outstanding, shares for basic earnings per share
  32,906   32,774   32,877   32,727 
Weighted-average stock options outstanding (b)
  25   11   30   13 
Shares for diluted earnings per share
  32,931   32,785   32,907   32,740 
Net earnings per common share, basic
 $1.04  $0.58  $3.14  $2.68 
Net earnings per common share, diluted
 $1.03  $0.58  $3.14  $2.68 
 
(a)
Participating securities include options, PSUs and RSUs that receive non-forfeitable dividends. Net earnings were allocated to 532,000 and 545,000 participating securities for the three and nine months ended September 30, 2011, respectively, and 597,000 and 629,000 participating securities for the three and nine months ended September 30, 2010.
(b)
For the calculation of diluted earnings per share, the Company uses the more dilutive of either the treasury stock method or the two-class method, to determine the weighted average number of outstanding common shares.  In addition, the Company had 741,000 and 733,000 weighted options and performance stock units for the three and nine months ended September 30, 2011, respectively, and 764,000 and 775,000 weighted options outstanding for the three and nine months ended September 30, 2010, respectively, which were anti-dilutive and therefore not included in the diluted earnings per share calculation.