Leases - Summary of Lease Costs (Detail) - USD ($) $ in Thousands	12 Months Ended
	Apr. 30, 2021	Apr. 30, 2020
Lease Cost [Abstract]
Operating lease costs	$ 926	$ 743
Finance Lease Costs		54
Short-term lease costs	13	13
Variable lease costs	149	47
Total lease costs	$ 1,088	$ 857