Subsequent Events - Additional Information (Detail) (USD $)
9 Months Ended
Sep. 30, 2012
Oct. 22, 2012
Subsequent Event
Subsequent Event [Line Items]    
Dividend payable, declaration date Oct. 22, 2012  
Dividend payable, amount   $ 0.27
Dividend payable, payable date Nov. 07, 2012  
Dividend payable, record date Nov. 01, 2012