Repurchase of Common Stock - Additional Information (Detail) In Millions, unless otherwise specified	Dec. 31, 2012
Equity, Class of Treasury Stock [Line Items]
Repurchase of common stock, additional authorized shares	2.4

The number of shares authorized to be repurchased by an entity's Board of Directors under a stock repurchase plan.

No definition available.

Name:	us-gaap_StockRepurchaseProgramNumberOfSharesAuthorizedToBeRepurchased
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant