v2.4.0.6
Preferred Stock - Additional Information (Detail) (USD $)
In Millions, except Share data, unless otherwise specified
 9 Months Ended 1 Months Ended
Sep. 30, 2012
Dec. 31, 2011
Jan. 31, 2012
Series A Preferred Stock
Noncumulative Preferred Stock
Jan. 31, 2012
Series A Preferred Stock
Noncumulative Preferred Stock
Minimum
Jun. 30, 2012
Series B Preferred Stock
Noncumulative Preferred Stock
Fixed Rate
Jun. 30, 2012
Series B Preferred Stock
Noncumulative Preferred Stock
Minimum
Fixed Rate
Class of Stock [Line Items]            
Preferred stock, shares authorized 9,940,000 9,940,000        
Preferred stock, par value $ 0.01 $ 0.01        
Depositary shares of non-cumulative perpetual preferred stock         19,400,000  
Ownership interest percentage in a share of 6.00% non-cumulative perpetual preferred stock         2.50%  
Value per depositary share         $ 25  
Net proceeds from issuance of preferred stock offerings $ 863   $ 394   $ 469  
Fixed dividend rate on preferred stock     7.00%   6.00%  
Preferred stock earliest redemption date       Feb. 01, 2022   Sep. 01, 2017
Fixed-to-floating rate non-cumulative perpetual preferred stock issued     400,000      
End date of fixed dividend rate on Preferred stock     2022-02      
Floating rate on 3-month LIBOR plus     4.82%