Stock-based Payments - Stock Option Activity (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Apr. 30, 2022	Apr. 30, 2021	Apr. 30, 2020
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Outstanding, Beginning Balance (in shares)	1,653,646	2,271,658
Granted (in shares)	166,052	135,834
Exercised (in shares)	(108,375)	(687,338)
Canceled (in shares)	(11,209)	(48,674)
Forfeited (in shares)	(36,875)	(12,000)
Expired (in shares)	(5,000)	(5,834)
Outstanding, Ending Balance (in shares)	1,658,239	1,653,646	2,271,658
Vested and expected to vest (in shares)	1,658,239	1,653,646
Vested (in shares)	1,354,479	1,332,854
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding, Weighted Average Exercise Price [Abstract]
Weighted Average Exercise Price, Outstanding, Beginning Balance (in usd per share)	$ 3.96	$ 3.23
Weighted Average Exercise Price, Granted (in usd per share)	9.44	9.24
Weighted Average Exercise Price, Exercised (in usd per share)	2.29	2.33
Weighted Average Exercise Price, Canceled (in usd per share)	4.71	6.03
Weighted Average Exercise Price, Forfeited (in usd per share)	7.45	7.48
Weighted Average Exercise Price, Expired (in usd per share)	9.60	10.80
Weighted Average Exercise Price, Outstanding, Ending Balance (in usd per share)	4.51	3.96	$ 3.23
Weighted Average Exercise Price, Vested and Expected to Vest (in usd per share)	4.51	3.96
Weighted Average Exercise Price, Vested (in usd per share)	$ 3.93	$ 3.34
Weighted Average Remaining Contractual Term, Outstanding, Beginning Balance (in years)		5 years 4 months 24 days	5 years
Weighted Average Remaining Contractual Life, Granted	9 years 3 months 18 days	7 years 3 months 18 days
Weighted Average Remaining Contractual Term, Outstanding, Ending Balance (in years)	4 years 10 months 24 days	5 years 4 months 24 days
Weighted Average Remaining Contractual Life (Years), Vested and expected to vest	4 years 10 months 24 days	5 years 4 months 24 days
Weighted Average Remaining Contractual Life (Years), Vested	4 years 2 months 12 days	4 years 9 months 18 days
Aggregate Intrinsic Value, Outstanding, Beginning Balance	$ 11,384	$ 10,663
Aggregate Intrinsic Value, Granted	0	259
Aggregate Intrinsic Value, Outstanding, Ending Balance	6,131	11,384	$ 10,663
Aggregate Intrinsic Value, Vested and expected to vest	6,131	11,384
Aggregate Intrinsic Value, Vested	$ 5,778	$ 9,995
Directors and Employees
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Outstanding, Beginning Balance (in shares)	1,618,231	2,228,326
Granted (in shares)	155,552	135,834
Exercised (in shares)	(108,375)	(686,178)
Canceled (in shares)	(11,209)	(47,751)
Forfeited (in shares)	(36,875)	(12,000)
Expired (in shares)	0	0
Outstanding, Ending Balance (in shares)	1,617,324	1,618,231	2,228,326
Vested and expected to vest (in shares)	1,617,324	1,618,231
Vested (in shares)	1,349,895	1,323,270
Non- Employees
Share-based Compensation Arrangement by Share-based Payment Award, Options, Outstanding [Roll Forward]
Outstanding, Beginning Balance (in shares)	35,415	43,332
Granted (in shares)	10,500	0
Exercised (in shares)	0	(1,160)
Canceled (in shares)	0	(923)
Forfeited (in shares)	0	0
Expired (in shares)	(5,000)	(5,834)
Outstanding, Ending Balance (in shares)	40,915	35,415	43,332
Vested and expected to vest (in shares)	40,915	35,415
Vested (in shares)	4,584	9,584