Stock-Based Compensation - Summary of Option Activity (Detail) - USD ($)	12 Months Ended
	Apr. 30, 2020	Apr. 30, 2019
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Shares, Outstanding Beginning Balance	1,739,338
Shares, Exercised	(37,494)
Shares, Granted	586,500
Shares, Cancelled	(12,667)
Shares, Outstanding Ending Balance	2,275,677	1,739,338
Shares, Exercisable	1,157,171
Shares, Vested and expected to vest	2,275,677
Weighted Average Exercise Price, Outstanding Beginning Balance	$ 9.95
Weighted Average Exercise Price, Exercised	4.39
Weighted Average Exercise Price, Granted	22.90
Weighted Average Exercise Price, Cancelled	19.89
Weighted Average Exercise Price, Outstanding Ending Balance	13.32	$ 9.95
Weighted Average Exercise Price, Exercisable	9.73
Weighted Average Exercise Price, Vested and expected to vest	$ 13.32
Weighted Average Remaining Contractual Life, Outstanding	7 years 9 months 29 days	8 years 5 months 19 days
Weighted Average Remaining Contractual Life, Exercisable	7 years 3 months
Weighted Average Remaining Contractual Life, Vested and expected to vest	7 years 9 months 29 days
Aggregate Intrinsic Value, Outstanding Beginning Balance	$ 22,807
Aggregate Intrinsic Value, Outstanding Ending Balance	4,899	$ 22,807
Aggregate Intrinsic Value, Exercisable	3,931
Aggregate Intrinsic Value, Vested and expected to vest	$ 4,899