Contingencies and Litigation - Additional Information (Detail) (USD $) In Millions, unless otherwise specified	Feb. 28, 2013	Aug. 31, 2012
Commitments and Contingencies Disclosure [Abstract]
Outstanding letters of credit	$ 10.8	$ 8.5
Discounted present value of future minimum lease payments	$ 12.2

The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

No definition available.

Name:	us-gaap_LettersOfCreditOutstandingAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant