Annual report pursuant to Section 13 and 15(d)

Shareholders' Equity - Additional Information (Detail)

v2.4.0.6
Shareholders' Equity - Additional Information (Detail) (USD $)
Share data in Millions, except Per Share data, unless otherwise specified
 1 Months Ended 3 Months Ended 12 Months Ended
Jul. 31, 2012
Jun. 30, 2012
May 31, 2012
Mar. 31, 2012
Jun. 30, 2011
Sep. 30, 2010
Jun. 30, 2010
Dec. 31, 2012
Dec. 31, 2011
Dec. 31, 2010
Jul. 30, 2012
May 03, 2010
Apr. 30, 2009
Stockholders Equity [Line Items]                          
Common shares, shares outstanding               106.9 115.8 117.8      
Preference shares authorized               7.5          
Preference shares par value               $ 0.002          
Cash dividend per common share       $ 0.30 $ 0.20 $ 0.13 $ 0.10            
Increase in cash dividends per common share       $ 0.10 $ 0.07 $ 0.03              
Dividends paid               $ 135,091,000 $ 85,489,000 $ 53,740,000      
Share repurchase program capacity authorization                     1,000,000,000 1,000,000,000 300,000,000
Previous expiration date of share repurchase program               Apr. 01, 2011          
Revised expiration date of share repurchase program               Dec. 01, 2014          
Repurchase of common stock     427,900,000         556,727,000 321,639,000 160,008,000      
Agreement expiration date               July 27, 2012          
Repurchase of common stock 3.9 5.3           11.0 5.5 5.7      
Share repurchase program, remaining authorized capacity               950,000,000          
Shares repurchased through open market purchases, aggregate cost               $ 527,800,000 $ 298,800,000 $ 150,100,000      
Average cost per share of shares repurchased               $ 47.78 $ 54.27 $ 26.13