v2.4.0.6
Equity (Details) (USD $)
In Millions, except Share data, unless otherwise specified
 12 Months Ended 1 Months Ended 12 Months Ended 19 Months Ended 1 Months Ended 12 Months Ended 12 Months Ended
Dec. 31, 2011
Dec. 31, 2010
Dec. 31, 2009
Dec. 31, 2011
Common Shares
Y
Dec. 31, 2010
Common Shares
Jun. 30, 2010
Common Shares
Dec. 31, 2011
Common Shares
Dec. 31, 2011
Common Shares
Nov. 30, 2010
Mandatory convertible preference shares
Dec. 31, 2010
Mandatory convertible preference shares
Dec. 31, 2009
Mandatory convertible preference shares
Dec. 31, 2011
Convertible perpetual preference shares
D
Dec. 31, 2010
Convertible perpetual preference shares
Equity Disclosures                          
Repurchase of entity issued and outstanding common shares approved by the Board of Directors           $ 700              
Extension period of share repurchase program (in years)       1                  
Repurchase of common shares 1,933,286 6,714,573     6,714,573   1,933,286 8,647,859          
Repurchase of common shares 120 354     354   120 474          
Issuance of common shares:                          
Issue of additional shares for conversion         1,702,642                
Conversion of mandatory convertible preference shares         8,417,215                
Preference shares outstanding                 862,455   862,455 6,900,000 6,900,000
Convertible preference share, number of common shares issued upon conversion                   9.7596      
Preference shares, par value (in dollars per share)                 $ 0.01     $ 0.01 $ 0.01
Preference shares, liquidation preference (in dollars per share)                 $ 1,000     $ 100 $ 100
Convertible preference share, common shares issued upon conversion, at any time before mandatory conversion date                 8.2416     1.0991  
Convertible preference shares accrued dividends (as a percent)                   5.125%   4.875%  
Dividends paid in cash $ 34 $ 67 $ 78           $ 44     $ 34 $ 34
Accumulated unpaid dividends up to a maximum additional (in dollars per share)                       $ 25  
Conversion price, convertible preference share (in dollars per share)                       $ 90.9802  
Convertible preference shares, aggregate common shares issued if converted at current conversion rate                 7,108,009     7,583,790  
Target ratio of closing share price to conversion price as a condition for conversion or redemption of Convertible Notes (as a percent)                       130.00%  
Minimum number of trading days triggering conversion or redemption feature                       20  
The maximum period of consecutive trading days that the entity's common stock closing price to conversion price must exceed a specified percentage of conversion price to trigger conversion or redemption feature of notes                       30