Subsequent Events - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	1 Months Ended
	Oct. 22, 2012	Dec. 31, 2011
Subsequent Event [Line Items]
Increase in share repurchase authorized amount		$ 50.0
Stock Repurchase Program
Subsequent Event [Line Items]
Increase in share repurchase authorized amount	$ 200.0	$ 50.0