Subsequent Event - Additional Information (Detail) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended		6 Months Ended		1 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012	Jul. 17, 2013 Subsequent Event	Jul. 17, 2013 Subsequent Event Dividend Declared
Subsequent Event [Line Items]
Authorized increase to share repurchase program					$ 500.0
Dividends declared	$ 0.36	$ 0.31	$ 0.72	$ 0.62		$ 0.36
Dividend payable date						Sep. 20, 2013
Dividend payable, stockholders of record date						Aug. 28, 2013
Dividend declared date						Jul. 17, 2013