Market Value and Maturities of Marketable Securities (Detail) - USD ($) $ in Thousands |
Apr. 30, 2017 |
Jul. 31, 2016 |
|---|---|---|
| Schedule of Available-for-sale Securities [Line Items] | ||
| Due in less than one year | $ 33,979 | $ 25,257 |
| Due in 1 to 3 years | 22,048 | 31,099 |
| Total marketable securities | $ 56,027 | $ 56,356 |