Quarterly Financial Data (Unaudited) - Additional Information (Detail) (Series A Preferred Stock [Member], USD $) In Millions, unless otherwise specified	3 Months Ended	12 Months Ended
Aug. 31, 2012	Aug. 31, 2012
Series A Preferred Stock [Member]
Quarterly Financial Data [Line Items]
Stock redeemed	$ 28.9
Original issue price of preferred stock	23.5
Accrued dividends	5.4	5.4
Accelerated discount accretion	3.2	5.5
Amortization of issuance costs	$ 0.6

Carrying value as of the balance sheet date of dividends declared but unpaid on equity securities issued by the entity and outstanding.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 944

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.15(5))

-URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 942

-SubTopic 210

-Section S99

-Paragraph 1

-Subparagraph (SX 210.9-03.15(5))

-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 15

-Subparagraph a

-Article 7

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Regulation S-X (SX)

-Number 210

-Section 03

-Paragraph 15

-Subparagraph 5

-Article 9

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Balance Type:	credit
Period Type:	instant