Summary Of Significant Accounting Policies (Summary Of Estimated Fair Value Of Financial Instruments) (Details) (USD $) In Thousands, unless otherwise specified	Apr. 30, 2012		Jul. 31, 2011		Apr. 30, 2011
Debt Instrument [Line Items]
Carrying Value	$ 490,876		$ 491,743		$ 535,836
6.50% Notes [Member]
Debt Instrument [Line Items]
Carrying Value	390,000	[1]	390,000	[1]	390,000	[1]
Fair Value	408,038
6.75% Notes [Member]
Debt Instrument [Line Items]
Carrying Value					43,937
Industrial Development Bonds [Member]
Debt Instrument [Line Items]
Carrying Value	41,200		41,200		41,200
Fair Value	47,712
Other Long-Term Debt [Member]
Debt Instrument [Line Items]
Carrying Value	7,101
Fair Value	$ 7,378

[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.