Taxes - Additional Information (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jan. 31, 2013	Jan. 31, 2012	Jan. 31, 2013	Jan. 31, 2012	Jul. 31, 2012
Income Taxes [Line Items]
Discrete tax benefit for federal research and experimentation credit	$ 466		$ 466
Statutory income tax rate	35.00%		35.00%
Income tax refund received		12,007
Income Tax expense benefit	3,592	(8,869)	5,740	(7,000)
Professional fees related to refund of Tax		2,714		2,714
Unrecognized tax benefit	794		794
Unrecognized tax benefits, accrued interest and penalties	712		712		640
Income Tax Refund
Income Taxes [Line Items]
Income Tax expense benefit		10,025		10,025
Reversal and Re-Measurement of Tax Reserves
Income Taxes [Line Items]
Income Tax expense benefit		$ 2,308		$ 2,308