Management representation - Additional Information (Detail) (Authorization of Equity Repurchase) In Millions, unless otherwise specified	Apr. 19, 2012
Authorization of Equity Repurchase
Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items]
Authorization to repurchase common shares, number of shares	16.0

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