Guarantor Subsidiaries - Additional Information (Detail) (USD $)	Aug. 31, 2012 Convertible Notes 2% Converitble Notes	Aug. 31, 2011 Convertible Notes 2% Converitble Notes	Nov. 30, 2003 Convertible Notes 2% Converitble Notes	Aug. 31, 2013 Senior Notes 5.625% Senior Notes	Aug. 31, 2012 Senior Notes 5.625% Senior Notes	Apr. 16, 2012 Senior Notes 5.625% Senior Notes	Aug. 31, 2012 Senior Notes 6.875% Senior Notes	Apr. 16, 2012 Senior Notes 6.875% Senior Notes
Debt Instrument [Line Items]
Long-term debt			$ 150,000,000.0	$ 300,000,000		$ 300,000,000.0		$ 250,000,000
Debt instrument, interest rate	2.00%	2.00%	2.00%	5.625%	5.625%	5.625%	6.875%	6.875%

The stated principal amount of the debt instrument at time of issuance, which may vary from the carrying amount because of unamortized premium or discount.

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 835

-SubTopic 30

-Section 45

-Paragraph 2

-URI http://asc.fasb.org/extlink&oid=6451184&loc=d3e28551-108399

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 835

-SubTopic 30

-Section 55

-Paragraph 8

-URI http://asc.fasb.org/extlink&oid=6584090&loc=d3e28878-108400

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher AICPA

-Name Accounting Principles Board Opinion (APB)

-Number 21

-Paragraph 16, 20

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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