Summary of Interest Expense Related to Convertible Notes (Detail) - 5.25% Convertible Senior Notes due 2019 - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Apr. 30, 2016	Apr. 30, 2015	Apr. 30, 2016	Apr. 30, 2015
Non Cash Convertible Debt Related Expense [Line Items]
Debt instrument, interest expense	$ 2,836	$ 2,549	$ 8,174	$ 7,532
Coupon Interest
Non Cash Convertible Debt Related Expense [Line Items]
Debt instrument, interest expense	1,322	1,313	3,968	3,939
Accretion of debt discount
Non Cash Convertible Debt Related Expense [Line Items]
Debt instrument, interest expense	1,391	1,136	3,864	3,305
Amortization of debt issue cost
Non Cash Convertible Debt Related Expense [Line Items]
Debt instrument, interest expense	$ 123	$ 100	$ 342	$ 288