Income Taxes - Additional Information (Detail) - USD ($)	3 Months Ended
	Oct. 31, 2017	Oct. 31, 2016	Jul. 31, 2017
Income Taxes [Line Items]
U.S. Federal statutory tax rate	35.00%	35.00%
Discrete tax benefit	$ 500,000
Unrecognized tax benefits, accrued interest and penalties	100,000		$ 100,000
Unrecognized tax benefits, for uncertain tax positions	$ 4,900,000
Maximum
Income Taxes [Line Items]
Discrete tax benefit		$ 100,000