Derivative Financial Instruments (Details) (USD $) In Thousands, unless otherwise specified	Jul. 31, 2012	Jul. 31, 2011
Fair value and presentation of derivatives
Asset Derivatives	$ 25	$ 2,978
Liability Derivatives	1,820	431
Foreign Exchange Contracts [Member] | Derivatives not designated as hedging instruments [Member] | Accrued Liabilities [Member]
Fair value and presentation of derivatives
Liability Derivatives	1,820
Foreign Exchange Contracts [Member] | Derivatives not designated as hedging instruments [Member] | Other Current Assets [Member]
Fair value and presentation of derivatives
Asset Derivatives	25	2,978
Commodity Future Contracts [Member] | Derivatives not designated as hedging instruments [Member] | Accrued Liabilities [Member]
Fair value and presentation of derivatives
Liability Derivatives		431
Commodity Future Contracts [Member] | Derivatives not designated as hedging instruments [Member] | Other Current Assets [Member]
Fair value and presentation of derivatives
Asset Derivatives