Leases (Details) - USD ($)		3 Months Ended			6 Months Ended
	Jun. 30, 2020	Oct. 31, 2020	Jul. 31, 2020	Oct. 31, 2019	Oct. 31, 2020	Oct. 31, 2019	Jun. 01, 2020	Apr. 30, 2020
Lessee, Lease, Description [Line Items]
Operating leases, rent expense		$ 314,000		$ 239,000	$ 629,000	$ 477,000
Operating lease right-of-use assets, net		$ 5,527,000			5,527,000			$ 2,798,000
Gain (loss) on termination of lease					$ 75,000	0
Weighted average remaining lease term (in years)		8 years 2 months 12 days			8 years 2 months 12 days
Discount rate (in percent)		6.08%			6.08%
Corporate Headquarters
Lessee, Lease, Description [Line Items]
Operating leases, rent expense		$ 24,000		24,000	$ 44,000	47,000
Rockville, MD
Lessee, Lease, Description [Line Items]
Operating leases, rent expense		290,000		151,000	534,000	302,000
Operating lease right-of-use assets, net			$ 118,000				$ 3,800,000
Operating lease liability			125,000				$ 3,800,000
Incremental rent expense			$ 8,000
Rockville, MD New Location
Lessee, Lease, Description [Line Items]
Operating leases, rent expense		$ 0		$ 64,000	$ 43,000	$ 128,000
Operating lease right-of-use assets, net	$ 850,000
Operating lease liability	926,000
Gain (loss) on termination of lease	$ 76,000