Leases (Details) - USD ($) $ in Thousands		3 Months Ended
	Jun. 30, 2020	Jul. 31, 2020	Jul. 31, 2019	Jun. 01, 2020	Apr. 30, 2020	May 01, 2019
Lessee, Lease, Description [Line Items]
Operating leases, rent expense		$ 307	$ 239
Operating lease right-of-use assets, net		5,673	3,103		$ 2,798
Gain (loss) on termination of lease		$ 75	0
Weighted average remaining lease term		8 years 5 months 1 day
Discount rate						6.10%
Corporate Headquarters
Lessee, Lease, Description [Line Items]
Operating leases, rent expense		$ 20	24
Rockville, MD
Lessee, Lease, Description [Line Items]
Operating leases, rent expense		244	151
Operating lease right-of-use assets, net		118		$ 3,800
Operating lease liability		125		$ 3,800
Incremental rent expense		8
Rockville, MD New Location
Lessee, Lease, Description [Line Items]
Operating leases, rent expense		$ 43	$ 64
Operating lease right-of-use assets, net	$ 850
Operating lease liability	926
Gain (loss) on termination of lease	$ 76