Fair Value of Financial Instruments (Details) - USD ($) $ in Thousands	Apr. 30, 2022	Apr. 30, 2021
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	$ 98,459	$ 81,720
Marketable securities	16,826	16,006
Total	115,285	97,726
Quoted Prices in Active Markets for Identical Assets (Level 1)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	98,459	81,720
Marketable securities	16,826	15,332
Total	115,285	97,052
Significant Other Observable Inputs (Level 2)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0	0
Marketable securities	0	674
Total	0	674
Significant Unobservable Inputs (Level 3)
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Cash equivalents	0	0
Marketable securities	0	0
Total	$ 0	$ 0