Long-Term Debt (Schedule Of Long-Term Debt) (Details) (USD $)	3 Months Ended						6 Months Ended				6 Months Ended							6 Months Ended		12 Months Ended											6 Months Ended
	Jan. 31, 2012		Jul. 31, 2011		Jan. 31, 2011		Jan. 31, 2012 Credit Facility Revolver [Member]		Jul. 31, 2011 Credit Facility Revolver [Member]	Jan. 31, 2011 Credit Facility Revolver [Member]	Jan. 31, 2012 Industrial Development Bonds [Member]		Jul. 31, 2011 Industrial Development Bonds [Member]	Jan. 31, 2011 Industrial Development Bonds [Member]	Jan. 31, 2012 Employee Housing Bonds [Member]	Jul. 31, 2011 Employee Housing Bonds [Member]	Jan. 31, 2011 Employee Housing Bonds [Member]	Jan. 31, 2012 6.50% Notes [Member]		Jul. 31, 2011 6.50% Notes [Member]	Apr. 25, 2011 6.50% Notes [Member]	Jan. 31, 2012 6.75% Notes [Member]		Jul. 31, 2011 6.75% Notes [Member]		Jan. 31, 2011 6.75% Notes [Member]		Jan. 31, 2012 Other [Member]	Jul. 31, 2011 Other [Member]	Jan. 31, 2011 Other [Member]	Jan. 31, 2012 Maximum [Member] Employee Housing Bonds [Member]	Jan. 31, 2012 Maximum [Member] Other [Member]	Jan. 31, 2012 Minimum [Member] Employee Housing Bonds [Member]		Jan. 31, 2012 Minimum [Member] Other [Member]
Schedule of Capitalization, Long-term Debt [Line Items]
Total debt	$ 491,360,000		$ 491,743,000		$ 497,757,000						$ 41,200,000		$ 41,200,000	$ 41,200,000	$ 52,575,000	$ 52,575,000	$ 52,575,000	$ 390,000,000		$ 390,000,000			[1]		[1]	$ 390,000,000	[1]	$ 7,585,000	$ 7,968,000	$ 13,982,000
Less: Current maturities	1,058,000	[2]	1,045,000	[2]	2,708,000	[2]
Long-term debt	490,302,000		490,698,000		495,049,000
Year of maturity	2019						2016	[3]			2020	[3]						2019	[1],[3]
Fiscal year maturity, start																																	2027	[3]	2012	[3]
Fiscal year maturity, end																															2039	2029
Debt instrument, stated percentage	6.50%																	6.50%				6.75%
Issuance of 6.50% senior subordinated notes																					$ 390,000,000
Long-term debt interest rate																				6.50%

[1] On April 25, 2011, the Company completed a private offering for $390.0 million of 6.50% Notes. Pursuant to the registration rights agreement executed as part of the offering of the 6.50% Notes, the Company agreed to file a registration statement for an exchange offer registered under the Securities Act of 1933. The registration statement was declared effective on November 16, 2011, and on November 17, 2011, the Company commenced its offer to exchange up to $390.0 million principal amount of newly issued 6.50% notes, registered under the Securities Act of 1933, for a like principal amount of its outstanding privately placed 6.50% Notes. The exchange offer expired on December 16, 2011 and all of the 6.50% Notes were tendered and exchanged for the new substantially identical registered notes.

[2] Current maturities represent principal payments due in the next 12 months.

[3] Maturities are based on the Company's July 31 fiscal year end.