Quarterly report pursuant to Section 13 or 15(d)

Capital Stock (Detail)

v2.4.0.6
Capital Stock (Detail) (USD $)
In Millions, except Share data, unless otherwise specified
 1 Months Ended 6 Months Ended
Jun. 01, 2012
Apr. 27, 2012
Mar. 13, 2012
Mar. 01, 2012
Feb. 15, 2012
Dec. 01, 2011
Nov. 18, 2011
Sep. 01, 2011
Aug. 15, 2011
Jul. 12, 2011
Jun. 13, 2011
Jun. 01, 2011
Apr. 29, 2011
Mar. 01, 2011
Feb. 15, 2011
Jun. 30, 2011
Jun. 30, 2012
Dec. 31, 2011
May 25, 2011
Dividend payable, per share $ 0.625         $ 0.280   $ 0.280       $ 0.140   $ 0.140          
Common share dividends date paid Jun. 01, 2012     Mar. 01, 2012   Dec. 01, 2011   Sep. 01, 2011       Jun. 01, 2011   Mar. 01, 2011          
Common share dividends date of record   Apr. 27, 2012     Feb. 15, 2012   Nov. 18, 2011   Aug. 15, 2011       Apr. 29, 2011   Feb. 15, 2011        
Percentage increase in dividends payable     123.00%             100.00%                  
Issuance of common shares (in shares)                     10,350,000                
Common shares, issued                                 149,195,469 149,195,469  
Proceeds from issuance of common stock                               $ 853.7      
Closing price per share                               $ 85.63      
Common shares, authorized                                 400,000,000 400,000,000 224,000,000
Total shares, authorized                                     231,000,000
Maximum [Member]
                                      
Common shares, authorized                                     400,000,000
Total shares, authorized                                     407,000,000
Common Shares [Member]
                                      
Common shares, issued                               9,000,000      
Over Allotment Option [Member]
                                      
Common shares, issued                               1,350,000      
Preferred Class A [Member]
                                      
Preferred stock, shares included in amendment                                     3,000,000
Preferred Class B [Member]
                                      
Preferred stock, shares included in amendment                                     4,000,000