Income Taxes - Additional Information (Details) - USD ($) $ in Thousands	12 Months Ended
	Apr. 30, 2021	Apr. 30, 2020	Apr. 30, 2019
Income Tax Disclosure [Line Items]
Effective income tax rate	8.60%	1.00%	11.00%
Tax benefits realized from the recognition of stock option deductions	$ 763	$ 878	$ 298
Foreign net operating loss carryforwards	3,141	0
Unrecognized tax benefits that, if recognized, would impact effective tax rate	25	34	43
Liability for potential penalties and interest	15	19
Research and development state tax credits	640	703	678
State and Local Jurisdiction
Income Tax Disclosure [Line Items]
Operating loss carryforwards	$ 3,400
Operating loss carryforwards expiration year	2036
Research and development state tax credits	$ 555	$ 427	$ 488
Foreign Tax Authority
Income Tax Disclosure [Line Items]
Operating loss carryforwards	$ 16,200