Fair Value of Financial Assets and Liabilities - Summary of Cash and Cash Equivalents (Details) - USD ($) $ in Thousands |
Jul. 31, 2017 |
Apr. 30, 2017 |
|---|---|---|
| Cash and Cash Equivalents [Line Items] | ||
| Total cash and cash equivalents | $ 47,016 | $ 52,494 |
| Demand deposit accounts | ||
| Cash and Cash Equivalents [Line Items] | ||
| Total cash and cash equivalents | 39,509 | 46,164 |
| Money market funds | ||
| Cash and Cash Equivalents [Line Items] | ||
| Total cash and cash equivalents | 3,660 | 3,532 |
| Commercial paper | ||
| Cash and Cash Equivalents [Line Items] | ||
| Total cash and cash equivalents | $ 3,847 | $ 2,798 |