Income Taxes - Unrecognized Tax Benefits (Details) - USD ($) $ in Thousands	12 Months Ended
	Apr. 30, 2021	Apr. 30, 2020
Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward]
Balance as of May 1	$ 4,048	$ 3,037
Increases for tax positions related to the current year	1,285	1,011
Balance as of April 30	$ 5,333	$ 4,048