Fair Value of Financial Assets and Liabilities - Summary of Cash and Cash Equivalents (Details) - USD ($) $ in Thousands |
Apr. 30, 2017 |
Apr. 30, 2016 |
|---|---|---|
| Cash and Cash Equivalents [Line Items] | ||
| Total cash and cash equivalents | $ 52,494 | $ 43,963 |
| Demand deposit accounts | ||
| Cash and Cash Equivalents [Line Items] | ||
| Total cash and cash equivalents | 46,164 | 38,692 |
| Money market funds | ||
| Cash and Cash Equivalents [Line Items] | ||
| Total cash and cash equivalents | 3,532 | 922 |
| Commercial paper | ||
| Cash and Cash Equivalents [Line Items] | ||
| Total cash and cash equivalents | $ 2,798 | $ 4,349 |