Summary of Significant Accounting Policies (Summary Of Estimated Fair Value Of Financial Instruments) (Details) (USD $) In Thousands, unless otherwise specified	Jul. 31, 2012	Jul. 31, 2011
Carrying value	$ 489,775	$ 490,698
6.50% Notes [Member]
Carrying value	390,000	390,000
Fair value	417,300	397,800
Industrial Development Bonds [Member]
Carrying value	41,200	41,200
Fair value	49,267	47,581
Other Long-Term Debt [Member]
Carrying value	6,990	7,968
Fair value	$ 7,821	$ 8,320

This element represents the portion of the balance sheet assertion valued at fair value by the entity whether such amount is presented as a separate caption or as a parenthetical disclosure. Additionally, this element may be used in connection with the fair value disclosures required in the footnote disclosures to the financial statements. The element may be used in both the balance sheet and disclosure in the same submission.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 825

-SubTopic 10

-Section 50

-Paragraph 10

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=7491637&loc=d3e13433-108611

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 825

-SubTopic 10

-Section 50

-Paragraph 12

-URI http://asc.fasb.org/extlink&oid=7491637&loc=d3e13476-108611

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