Restatement of Previously Issued Financial Statements - Additional Information (Detail) (Restatement Pricing Adjustments, USD $)	3 Months Ended		6 Months Ended
	Jan. 31, 2013	Jan. 31, 2012	Jan. 31, 2013	Jan. 31, 2012
Restatement Pricing Adjustments
Condensed Financial Statements, Captions [Line Items]
Derecognized accrued pricing liabilities resulted from restatement adjustments	$ 0	$ 0	$ 0	$ 0
Decrease in revenues		300,000		500,000
Change in net income		$ 300,000		$ 300,000
Change in basic earnings per share resulted from restatement adjustments		$ 0.01		$ 0.01
Change in diluted earnings per share resulted from restatement adjustments		$ 0.01		$ 0.01