Fair Value Measurements - Financial Assets and Liabilities Accounted for at Fair Value on Recurring Basis (Detail) (USD $) In Thousands, unless otherwise specified	9 Months Ended					3 Months Ended	9 Months Ended	3 Months Ended	9 Months Ended							3 Months Ended	9 Months Ended	3 Months Ended	9 Months Ended							3 Months Ended	9 Months Ended	3 Months Ended	9 Months Ended
	Apr. 30, 2013	Apr. 30, 2012	Jul. 31, 2012	Apr. 30, 2013 Other Assets [Member]	Jul. 31, 2012 Other Assets [Member]	Jul. 31, 2012 Prepaid expenses and other current assets [Member]	Apr. 30, 2013 Prepaid expenses and other current assets [Member]	Jul. 31, 2012 Other current liabilities [Member]	Apr. 30, 2013 Other current liabilities [Member]	Apr. 30, 2013 Long term obligations less current maturities [Member]	Jul. 31, 2012 Long term obligations less current maturities [Member]	Apr. 30, 2013 Fair Value, Inputs, Level 1 [Member]	Jul. 31, 2012 Fair Value, Inputs, Level 1 [Member]	Apr. 30, 2013 Fair Value, Inputs, Level 1 [Member] Other Assets [Member]	Jul. 31, 2012 Fair Value, Inputs, Level 1 [Member] Other Assets [Member]	Jul. 31, 2012 Fair Value, Inputs, Level 1 [Member] Prepaid expenses and other current assets [Member]	Apr. 30, 2013 Fair Value, Inputs, Level 1 [Member] Prepaid expenses and other current assets [Member]	Jul. 31, 2012 Fair Value, Inputs, Level 1 [Member] Other current liabilities [Member]	Apr. 30, 2013 Fair Value, Inputs, Level 1 [Member] Other current liabilities [Member]	Apr. 30, 2013 Fair Value, Inputs, Level 1 [Member] Long term obligations less current maturities [Member]	Jul. 31, 2012 Fair Value, Inputs, Level 1 [Member] Long term obligations less current maturities [Member]	Apr. 30, 2013 Fair Value, Inputs, Level 2 [Member]	Jul. 31, 2012 Fair Value, Inputs, Level 2 [Member]	Apr. 30, 2013 Fair Value, Inputs, Level 2 [Member] Other Assets [Member]	Jul. 31, 2012 Fair Value, Inputs, Level 2 [Member] Other Assets [Member]	Jul. 31, 2012 Fair Value, Inputs, Level 2 [Member] Prepaid expenses and other current assets [Member]	Apr. 30, 2013 Fair Value, Inputs, Level 2 [Member] Prepaid expenses and other current assets [Member]	Jul. 31, 2012 Fair Value, Inputs, Level 2 [Member] Other current liabilities [Member]	Apr. 30, 2013 Fair Value, Inputs, Level 2 [Member] Other current liabilities [Member]	Apr. 30, 2013 Fair Value, Inputs, Level 2 [Member] Long term obligations less current maturities [Member]	Jul. 31, 2012 Fair Value, Inputs, Level 2 [Member] Long term obligations less current maturities [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Trading securities				$ 14,614	$ 12,676									$ 14,614	$ 12,676									$ 0	$ 0
Foreign exchange contracts	(24)	(3,228)				1,234	1,242	281	438							0	0	0	0							1,234	1,242	281	438
Total Assets	15,856		13,910									14,614	12,676									1,242	1,234
Foreign currency denominated debt	359,427		338,668							108,001	99,081									0	0									108,001	99,081
Total Liabilities	108,439		99,362									0	0									108,439	99,362
Long term debt obligation at carrying value	$ 338,301		$ 316,208