Fair Value Measurements (Details Textual)	Jul. 31, 2011	Jul. 31, 2010
Fair Value Measurements (Textuals) [Abstract]
Interest on convertible notes	4.00%	4.00%
Four Percent Convertible Senior Notes Due 2015 [Member]
Fair Value Measurements (Textuals) [Abstract]
Interest on convertible notes	4.00%

Interest rate stated in the contractual debt agreement.

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher SEC
-Name Regulation S-X (SX)
-Number 210
-Section 02
-Paragraph 22
-Article 5

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

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Namespace Prefix:	us-gaap
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant