Subsequent Events - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	1 Months Ended
Jun. 06, 2012 Maximum	Aug. 17, 2011 Maximum	Oct. 31, 2012 Stock Repurchase Program
Subsequent Event [Line Items]
Stock repurchase authorized amount	$ 15	$ 25	$ 25

The amount authorized by an entity's Board of Directors under a stock repurchase plan.

No definition available.

Name:	us-gaap_StockRepurchaseProgramAuthorizedAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration