Financial Assets Measured at Fair Value on Recurring Basis and Classified by Fair Value Hierarchy (Detail) - Fair Value, Measurements, Recurring - Money market funds - USD ($) $ in Thousands	Oct. 31, 2018	Jul. 31, 2018
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, fair value disclosure, recurring	$ 29,494	$ 47,186
Fair Value, Inputs, Level 1
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Assets, fair value disclosure, recurring	$ 29,494	$ 47,186