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Earnings Per Share (Tables)
 12 Months Ended
Dec. 31, 2011
Earnings Per Share [Abstract]  
Calculation Of Earnings Per Share
The calculation of earnings per share is as follows:
$ in millions, except per share data
Net Income Attributable to Common Shareholders
 
Weighted Average Number of Shares
 
Per Share Amount
For the year ended December 31, 2011
 
 
 
 
 
Basic earnings per share

$729.7

 
462.9

 

$1.58

Dilutive effect of share-based awards
—

 
1.8

 
—

Diluted earnings per share

$729.7

 
464.7

 

$1.57

For the year ended December 31, 2010
 
 
 
 
 
Basic earnings per share

$465.7

 
460.4

 

$1.01

Dilutive effect of share-based awards
—

 
2.8

 
—

Diluted earnings per share

$465.7

 
463.2

 

$1.01

For the year ended December 31, 2009
 
 
 
 
 
Basic earnings per share

$322.5

 
417.2

 

$0.77

Dilutive effect of share-based awards
—

 
6.4

 
—

Diluted earnings per share

$322.5

 
423.6

 

$0.76