Earnings per Share (Tables)
 9 Months Ended
Sep. 30, 2014
Earnings per Share [Abstract]  
Computation of basic and diluted earnings per common share
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
  
Nine months ended
 
  
September 30,
  
September 30,
 
    
2014
  
2013
  
2014
  
2013
 
Numerator:
 
  
  
  
 
Net earnings
 
$
87.9
  
$
15.4
  
$
137.4
  
$
72.4
 
Less: net earnings allocated to participating securities (a)
  
(0.5
)
  
(0.1
)
  
(0.8
)
  
(0.6
)
Net earnings available to common shareholders
 
$
87.4
  
$
15.3
  
$
136.6
  
$
71.8
 
 
Denominator (in thousands):
                
Weighted-average common shares outstanding, shares for basic earnings per share
  
33,575
   
33,469
   
33,542
   
33,378
 
Weighted-average awards outstanding (b)
  
26
   
15
   
24
   
24
 
Shares for diluted earnings per share
  
33,601
   
33,484
   
33,566
   
33,402
 
Net earnings per common share, basic
 
$
2.60
  
$
0.46
  
$
4.07
  
$
2.15
 
Net earnings per common share, diluted
 
$
2.60
  
$
0.46
  
$
4.07
  
$
2.15
 

(a)
Participating securities include options, PSUs and RSUs that receive non-forfeitable dividends. Weighted participating securities included 209,000 and 214,000 for the three and nine months ended September 30, 2014, respectively, and 275,000 and 305,000 for the three and nine months ended September 30, 2013, respectively.
(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 389,000 and 397,000 weighted-awards outstanding for the three and nine months ended September 30, 2014, respectively, and 410,000 and 469,000 for the three and nine months ended September 30, 2013, respectively, which were anti-dilutive and therefore not included in the diluted earnings per-share calculation.