Fair Value Measurements - Additional Information (Detail) |
Apr. 30, 2019
USD ($)
|
|---|---|
| Fair Value Measurements Disclosure [Line Items] | |
| Marketable securities fair value, mature between one and three years | $ 4,600,000 |
| Fair Value, Inputs, Level 3 [Member] | |
| Fair Value Measurements Disclosure [Line Items] | |
| Fair value measurements of our financial assets | $ 0 |