Fair Value of Financial Assets and Liabilities - Summary of Cash and Cash Equivalents (Details) - USD ($) $ in Thousands |
Oct. 31, 2016 |
Apr. 30, 2016 |
|---|---|---|
| Cash and Cash Equivalents [Line Items] | ||
| Total cash and cash equivalents | $ 44,427 | $ 43,963 |
| Demand deposit accounts | ||
| Cash and Cash Equivalents [Line Items] | ||
| Total cash and cash equivalents | 34,656 | 38,692 |
| Money market funds | ||
| Cash and Cash Equivalents [Line Items] | ||
| Total cash and cash equivalents | 9,421 | 922 |
| Commercial paper | ||
| Cash and Cash Equivalents [Line Items] | ||
| Total cash and cash equivalents | $ 350 | $ 4,349 |