Market Value and Amortized Cost of Marketable Securities (Detail) - USD ($) $ in Thousands |
Apr. 30, 2017 |
Jul. 31, 2016 |
|---|---|---|
| Schedule of Available-for-sale Securities [Line Items] | ||
| Market Value | $ 56,027 | $ 56,356 |
| Amortized Cost | 55,895 | 56,065 |
| Corporate | ||
| Schedule of Available-for-sale Securities [Line Items] | ||
| Market Value | 24,722 | 22,574 |
| Amortized Cost | 24,586 | 22,405 |
| Government | ||
| Schedule of Available-for-sale Securities [Line Items] | ||
| Market Value | 13,657 | 18,321 |
| Amortized Cost | 13,677 | 18,249 |
| Collateralized Mortgage Backed Securities | ||
| Schedule of Available-for-sale Securities [Line Items] | ||
| Market Value | 2,327 | 1,665 |
| Amortized Cost | 2,326 | 1,672 |
| Asset-backed Securities | ||
| Schedule of Available-for-sale Securities [Line Items] | ||
| Market Value | 15,321 | 13,796 |
| Amortized Cost | $ 15,306 | $ 13,739 |