| **Long-Term Debt**             | 9 Months Ended                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                          |
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| **Debt Disclosure [Abstract]** |                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    |
| Long-Term Debt                 | Long-Term DebtLong-term debt as of April 30, 2013, July 31, 2012 and April 30, 2012 is summarized as follows (in thousands):   Maturity (a) April 30, 2013 July 31, 2012 April 30, 2012Credit Facility Revolver 2016 $— $— $—Industrial Development Bonds 2020 41,200 41,200 41,200Employee Housing Bonds 2027-2039 52,575 52,575 52,5756.50% Notes  2019 390,000 390,000 390,000Other 2013-2029 5,983 6,990 7,101Total debt   489,758 490,765 490,876Less: Current maturities (b)   518 990 1,119Long-term debt   $489,240 $489,775 $489,757 (a)Maturities are based on the Company’s July 31 fiscal year end.(b)Current maturities represent principal payments due in the next 12 months.Aggregate maturities for debt outstanding as of April 30, 2013 reflected by fiscal year are as follows (in thousands):   2013$92014509201553320162442017257Thereafter488,206  Total debt$489,758  The Company incurred gross interest expense of $8.4 million for both the three months ended April 30, 2013 and 2012, respectively, of which $0.5 million was amortization of deferred financing costs. The Company had no capitalized interest during the three months ended April 30, 2013 and 2012. The Company incurred gross interest expense of $25.3 million and $25.4 million for the nine months ended April 30, 2013 and 2012, respectively, of which $1.5 million was amortization of deferred financing costs in both years. The Company had no capitalized interest during the nine months ended April 30, 2013. The Company capitalized $0.1 million of interest during the nine months ended April 30, 2012. |

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| - Definition
The entire disclosure for information about short-term and long-term debt arrangements, which includes amounts of borrowings under each line of credit, note payable, commercial paper issue, bonds indenture, debenture issue, own-share lending arrangements and any other contractual agreement to repay funds, and about the underlying arrangements, rationale for a classification as long-term, including repayment terms, interest rates, collateral provided, restrictions on use of assets and activities, whether or not in compliance with debt covenants, and other matters important to users of the financial statements, such as the effects of refinancing and noncompliance with debt covenants.
+ References
Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.19,20,22) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 505 -SubTopic 10 -Section 50 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=6928386&loc=d3e21475-112644Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher SEC -Name Regulation S-X (SX) -Number 210 -Section 02 -Paragraph 19, 20, 22 -Article 5Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Statement of Financial Accounting Standard (FAS) -Number 129 -Paragraph 2, 4 -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.
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