Stockholders' Equity - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jan. 31, 2018	Jan. 31, 2017	Jan. 31, 2018	Jan. 31, 2017
Stock Based Compensation And Stockholders Equity [Line Items]
Total compensation expenses	$ 4,413	$ 3,154	$ 8,731	$ 5,892
Withholding taxes payable			7,657	4,572
Restricted Stock Units (RSUs)
Stock Based Compensation And Stockholders Equity [Line Items]
Withholding taxes payable			$ 7,657	$ 4,572