Summary of Interest Expense Related to Convertible Notes (Detail) (5.25% Convertible Senior Notes due 2019, USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Apr. 30, 2015	Apr. 30, 2014	Apr. 30, 2015	Apr. 30, 2014
Non Cash Convertible Debt Related Expense [Line Items]
Debt instrument, interest expense	$ 2,549	$ 1,149	$ 7,532	$ 1,149
Coupon interest rate
Non Cash Convertible Debt Related Expense [Line Items]
Debt instrument, interest expense	1,313	680	3,939	680
Accretion of debt discount
Non Cash Convertible Debt Related Expense [Line Items]
Debt instrument, interest expense	1,136	418	3,305	418
Amortization of debt issue cost
Non Cash Convertible Debt Related Expense [Line Items]
Debt instrument, interest expense	$ 100	$ 51	$ 288	$ 51