Leases - Narrative (Details) - USD ($) $ in Thousands	3 Months Ended
	Jul. 31, 2022	Jul. 31, 2021	Jul. 31, 2020	Apr. 30, 2022	Apr. 01, 2021	Jun. 01, 2020	Mar. 30, 2020
Lessee, Lease, Description [Line Items]
Operating leases, rent expense	$ 467	$ 452
Extension term							6 months
Operating lease right-of-use assets, net	7,971			$ 8,230
Present value of minimum lease payments	$ 9,226
Weighted average remaining lease term (in years)	6 years 5 months 1 day
Weighted average discount rate, percent	5.73%
Corporate Headquarters
Lessee, Lease, Description [Line Items]
Operating leases, rent expense	$ 21	24
Rockville, MD
Lessee, Lease, Description [Line Items]
Operating leases, rent expense	422	422
Operating lease right-of-use assets, net			$ 118			$ 3,800
Present value of minimum lease payments			125			$ 3,800
Incremental rent expense			$ 8
Additional Expansion Premises
Lessee, Lease, Description [Line Items]
Operating lease right-of-use assets, net					$ 3,300
Present value of minimum lease payments					$ 3,300
Milan Italy
Lessee, Lease, Description [Line Items]
Operating leases, rent expense	23	$ 0
Operating lease right-of-use assets, net	205
Present value of minimum lease payments	$ 205