Subsequent Event - Additional Information (Detail) (Dividend Declared, USD $)	1 Months Ended
	Oct. 01, 2012
Dividend Declared
Subsequent Event [Line Items]
Cash dividend declaration date	Oct. 01, 2012
Cash dividend declared on common stock, per share	$ 0.30
Cash dividend declared	$ 234,000,000
Cash dividend payable, date	Dec. 03, 2012
Dividend payment recorded date	Oct. 31, 2012